Over two thousand patients with psychiatric complaints and symptoms seek medical evaluation in the NMH ED each year. This includes known psychiatric patients (with and without medical complaints) and non-psychiatric patients with new psychiatric complaints or symptoms. Routine laboratory tests are obtained for most ED patients with psychiatric complaints or symptoms. The rationale for using these laboratory-screening tests is to rapidly exclude the possibility of secondary causes of psychosis in this subgroup of patients. However, the predictive value and cost-effectiveness of these screening tests have not been definitively established. We conducted a retrospective study of all patients aged 18-65 with potential psychiatric triage complaints or symptoms evaluated in our ED over a 4-month period. We found that medical co-morbidities are frequently seen in patients with psychiatric complaints and even in patients with known psychiatric histories and without initial medical complaints. Despite this finding, certain screening tests may not be needed in patients with prior psychiatric history and no medical complaints. This information can be used to limit the unnecessary laboratory testing of selected ED psychiatric patients.