OBJECTIVE: Psychiatric comorbidity in medical outpatients is associated with personal suffering and reduced psychosocial functioning. Simple clinical indicators are needed to improve recognition and treatment of psychiatric comorbidity. This study aimed to identify predictors of psychiatric comorbidity for diagnostic use in busy medical settings and to describe their criterion validity. METHODS: The SCID was adopted as the independent criterion standard for the presence of a psychiatric comorbidity in 357 patients (68% female; mean age, 43 years) of six internal medicine outpatient clinics and 12 general practices. Potential indicators of psychiatric comorbidity were investigated by means of patient and physician questionnaires. Logistic regression analyses were used to identify independent predictors of psychiatric comorbidity, and their operating characteristics were determined. RESULTS: Of 18 indicators, the four most important predictors of psychiatric comorbidity were identified: a screening question for nervousness, anxiety, or worries (odds ratio, 11.9; p