This study examined whether the Structured Clinical Interview for DSM (SCID), a widely used semistructured interview designed to assess psychopathology categorically, can be adapted to identify reliable and valid severity dimensions of psychopathology. The present study also examined whether these severity dimensions have better psychometric properties (internal consistency, test-retest reliability, and concurrent and predictive validity) than categorical diagnoses. Participants (N = 234) were recruited from the community and clinics. Retest reliability and prospective predictive validity (symptoms and functioning 1 year later) were examined in subsamples of participants. Dimensional severity scales were created from an adapted version of the SCID for both current and lifetime major depression, alcohol, substance, post-traumatic stress disorder, panic, agoraphobia, social anxiety, specific phobia, obsessive-compulsive disorder, and generalized anxiety disorder. The SCID’s severity scales demonstrated substantial internal consistency (all Cronbach’s $α$s textgreater.80), test-retest reliability, and concurrent and predictive validity. Symptom severity scales demonstrated significant incremental validity over and above categorical diagnoses for both current and prospective outcomes. The psychometric properties of SCID-identified symptom scales were far superior to the psychometrics of categorical diagnoses for both current and lifetime psychopathology. These results highlight the feasibility and utility of the SCID to assess reliable and valid symptom severity dimensions of both current and lifetime psychopathology.