We evaluated a set of diagnostic screens for mental disorders in primary care. A self-administered screening questionnaire containing 26 items testing for multiple mental disorders was completed by 1,001 patients. Brief diagnostic modules, structured for psychiatric diagnoses, were subsequently administered to each patient by a research nurse. Operating characteristics of the screens were as follows: alcohol dependence (sensitivity [SE] 0.75; positive predictive value [PPV] 0.58; [kappa] 0.63), drug dependence (SE 0.50; PPV 0.50; kappa 0.50), generalized anxiety disorder (SE 0.74; PPV 0.44; kappa 0.44), major depressive disorder (SE 0.71; PPV 0.52; kappa 0.50), obsessive compulsive disorder (SE 0.71; PPV 0.15; kappa 0.21), and panic disorder (SE 0.71; PPV 0.43; kappa 0.48). Other chance-corrected measures of agreement are also reported, and criterion validity of the screens is examined. The results provide evidence that the screens discriminate between patients with symptomatology meeting established diagnostic criteria and those without. They detected previously unrecognized cases in this study and may prove to be valuable tools for psychiatric diagnosis in primary care.