This study examined the relationship between criminal violence and type of substance abuse among 184 current and former residents of an inpatient non-hospital drug and alcohol treatment facility. The criminal justice system functioned as the source of referral into the program for 89% of the subjects studied while only 11% came to treatment voluntarily. Neither multiple regression, stepwise regression, nor factor analysis found criminal violence to be predicted by substance abuse, drug dealing activity, or a collection of demographic variables often theoretically linked to violence (i.e., youthfulness, having an early onset of criminal activity, and being male, minority, unmarried, and dually diagnosed). Alternatively, a significant link between poly-drug use and poly-criminality allude to shared underlying causal mechanisms for both substance abuse and violence. (Contains 4 tables.)