The Structured Clinical Interview for DSM-III, Axis I was administered to a consecutive series of 30 cocaine abusers entering outpatient treatment. Another mental disorder was diagnosed only if its onset occurred before the onset of any substance dependence disorder. Diagnoses were made on a lifetime basis without regard to hierarchy. Most cocaine abusers had one or more additional diagnoses. We propose a model of two subtypes of cocaine abusers: (1) a primary affective disorder group, which may be split into bipolar versus unipolar or into severely versus mildly depressed subgroups; and (2) a group with other drug dependencies. The small n, limited sample, and methodological problems with diagnosis in the setting of substance abuse make these findings tentative. Future research should combine larger diagnostic studies with treatment trials to test whether such diagnostic subtypes have prognostic or treatment implications.