“Clinical trial” is the scientific term for a test or study of a new drug, surgical procedure, or medical device in people, or new ways to use existing treatments. Clinical trials are part of clinical research and are at the heart of all medical advances. The goal of clinical trials is to determine if a new test or treatment works and is safe and effective for people to use. Doctors and other health professionals run the tests according to strict rules set by the Food and Drug Administration (FDA).  The FDA sets the rules to make sure that people who agree to be in the studies are treated as safely as possible.

Clinical trials can also look at other aspects of care, such as improving the quality of life for people with chronic illnesses.

Clinical research is medical research that involves people. People volunteer to participate in carefully conducted investigations that ultimately uncover better ways to treat, prevent, diagnose, and understand human disease. Clinical research includes trials that test new treatments and therapies, as well as long–term natural history studies, which provide valuable information about how disease and health progress.

People participate in clinical trials for a variety of reasons. Healthy volunteers say they participate to help others and to contribute to moving science forward. Participants with an illness or disease also participate to help others, but also to possibly receive the newest treatment and to have the additional care and attention from the clinical trial staff. Trials can also help others better understand how the treatment works in people of different races and genders. Clinical trials offer hope for many people and an opportunity to help researchers find better treatments for others in the future.

Many different types of people participate in clinical trials. Some are healthy, while others may have illnesses. A healthy volunteer is a person with no known significant health problems who participates in clinical research to test a new drug, device, or intervention. Research procedures with healthy volunteers are designed to develop new knowledge, not to provide direct benefit to study participants. Healthy volunteers have always played an important role in research.

Healthy volunteers are needed for several reasons. When developing a new technique, such as a blood test or imaging device, healthy volunteers (formerly called "normal volunteers") help define the limits of "normal." These volunteers serve as controls for patient groups and are often matched to patients on characteristics such as age, gender, or family relationship. They receive the same test, procedure, or drug the patient group receives. Investigators learn about the disease process by comparing the patient group to the healthy volunteers.

A patient volunteer has a known health problem and participates in research to better understand, diagnose, treat, or cure that disease or condition. Research procedures with a patient volunteer help develop new knowledge. These procedures may or may not benefit the study participants.

Patient volunteers may be involved in studies similar to those in which healthy volunteers participate. These studies involve drugs, devices, or interventions designed to prevent, treat, or cure disease. Although these studies may provide direct benefit to patient volunteers, the main aim is to prove, by scientific means, the effects and limitations of the experimental treatment. Consequently, some patients serve as controls by not taking the test drug, or by receiving test doses of the drug large enough only to show that it is present, but not at a level that can treat the condition. A study's benefits may be indirect for the volunteers but may help others.

All clinical trials have guidelines about who can participate, called Inclusion/Exclusion Criteria. Factors that allow someone to participate in a clinical trial are called "inclusion criteria." Those that exclude or not allow participation are called "exclusion criteria." These criteria are based on factors such as age, gender, the type and stage of a disease, previous treatment history, and other medical conditions. Before joining a clinical trial, a participant must qualify for the study. Some research studies seek participants with illnesses or conditions to be studied in the clinical trial, while others need healthy volunteers.

Some studies need both types. Inclusion and exclusion criteria are not used to reject people personally; rather, the criteria are used to identify appropriate participants and keep them safe, and to help ensure that researchers can find new information they need.

Here are some questions to ask your doctor to help you decide if you want to take part in a clinical trial:

The study

• What is the purpose of the study?
• Why do researchers think the approach may be effective?
• Who will fund the study? 
• Who has reviewed and approved the study? 
• How are study results and safety of participants being checked?
• How long will the study last? 
• What will be my responsibilities if I participate? 

Possible risks and benefits

• What are my possible short-term benefits?
• What are my possible long-term benefits?
• What are my short-term risks, such as side effects?
• What are my possible long-term risks? 
• What other options do people with my disease have?
• How do the possible risks and benefits of this trial compare with those options?

Participation and care

• What kinds of therapies, procedures and /or tests will I have during the trial?
• Will they hurt, and if so, for how long?
• How often does the study require me to go to the doctor or clinic?
• Will I be hospitalized? If so, how often and for how long?
• How do the tests in the study compare with those I would have outside of the trial?
• Will I be able to take my regular medications while in the clinical trial?
• Where will I have my medical care?
• Who will be in charge of my care?
• What follow-up will there be?
• What will happen at the end of the study?

Personal issues

• How could being in this study affect my daily life? 
• Can I talk to other people in the study?

Cost issues

• Will I have to pay for any part of the trial such as tests or the study drug?
• If so, what will the charges likely be?
• What is my health insurance likely to cover?
• Who can help answer any questions from my insurance company or health plan?
• Will there be any travel or child care costs that I need to consider while I am in the trial?

Tips for asking your doctor about trials

• Consider taking a family member or friend along, for support and for help in asking questions or recording answers.
• Plan ahead what to ask — but don't hesitate to ask any new questions you think of while you're there.
• Write down your questions in advance, to make sure you remember to ask them all.
• Write down the answers, so that you can review them whenever you want.
• Ask about bringing a tape recorder to make a taped record of what's said (even if you write down answers).

Some treatments that are being tested may have side effects that can be unpleasant, serious, or even life-threatening. Because the treatments being studied are new, doctors don’t always know what the side effects will be. Many side effects are temporary and go away when the treatment is stopped. But others can be permanent. Some side effects appear during treatment, while others may not show up until after the treatment is over. The risks depend on the treatment being studied and all known risks should be fully explained to you by the researchers.

Each clinical trial in the United States must be approved and monitored by an Institutional Review Board (IRB) to ensure that the risks are minimal and are worth any potential benefits. An IRB is an independent committee that consists of physicians, statisticians, and members of the community who ensure that clinical trials are ethical and that the rights of participants are protected. Federal regulation requires all institutions in the United States that conduct or support biomedical research involving people to have an IRB initially approve and periodically review the research.

Informed Consent

To help you decide if you want to be in a study, FDA requires that you be given complete information about the study before you agree to take part. This is known as informed  consent. FDA requires that people be told:

   • That the study involves research of an unproven drug or device

   • The purpose of the research

   • How long the study will take

   • What will happen in the study and which parts of the study are experimental

   • Possible risks or discomforts

   • Possible benefits

   • Other procedures or treatments that you might want to consider instead of the treatment being studied

   • That FDA may look at study records, but the records will be kept secret

   • Whether any medical treatments are available if you are hurt, what those treatments are, where they can be found, and who will pay for the treatment

   • The person to contact with questions about the study, your rights, or if you get hurt

   • You can quit at any time.

Informed consents must be written so you can understand it. If you don’t, be sure to ask the doctor or other medical person to explain it. Make sure you understand all of it before you agree to be in the study.

Before you can be in the study, you must sign the informed consent form, showing that you have been given this information and understand it. The informed consent form is NOT a contract and you can leave the study at any time, for any reason.

Institutional Review Board

Each clinical trial in the United States must be approved and monitored by an Institutional Review Board (IRB) to ensure that the risks are minimal and are worth any potential benefits. An IRB is an independent committee that consists of physicians, statisticians, and members of the community who ensure that clinical trials are ethical and that the rights of participants are protected. Federal regulation requires all institutions in the United States that conduct or support biomedical research involving people to have an IRB initially approve and periodically review the research.

For further reading about research protocols, see: 

• Office of Human Research Protection
• Children's Assent to Clinical Trial Participation

For more information on participants’ privacy and confidentiality, see:

• National Institutes of Health, HIPAA Privacy Rule

The Food and Drug Administration, FDA’s Drug Review Process:

• Ensuring Drugs Are Safe and Effective
• National Cancer Institute, Monitoring the Safety of Clinical Trials

These committees are used mainly when one treatment is being compared with another.  These committees are particularly important in tests of treatments for serious or life threatening disease. These experts review information from studies to make sure they are being done in a way that is safest for the volunteers. During a study, if the committee finds that the treatment is harmful or of no benefit, it will stop the study. If a study shows that one treatment works better than another, the committee stops the study and all volunteers are offered the better treatment.

After a clinical trial is completed, researchers carefully examine information collected during the study before making decisions about the meaning of the findings and about further testing. After a phase 1 or 2 trial, the researchers decide whether to move on to the next phase or to stop testing the agent or intervention because it was unsafe or ineffective. When a phase 3 trial is completed, the researchers examine the data and decide whether the results have medical importance.

Results from clinical trials are often published in peer-reviewed scientific journals. Peer review is a process by which experts review the report before it is published to ensure that the analysis and conclusions are sound. If the results are particularly important, they may be featured in news media and discussed at scientific meetings and by patient advocacy groups before they are published. Once a new approach has been proven safe and effective in a clinical trial, it may become the standard of medical practice.

Ask the research team members if the study results have been or will be published. Published study results are also available by searching for the study's official name or Protocol ID number in the National Library of Medicine's PubMed® database.