Married or cohabitating substance-abusing patients (N = 80) who were entering individual outpatient treatment, most of whom were referred by the criminal justice system (n = 68; 85%), were randomly assigned to a no-couples-treatment control group (n = 40) or to 12 weekly sessions of adjunctive behavioral couples therapy (BCT; n = 40). Drug use and relationship adjustment measures were collected at pretreatment, posttreatment, and at 3-, 6-, 9-, and 12-month follow-ups. Couples who received BCT as part of individual-based treatment had better relationship outcomes, in terms of more positive dyadic adjustment and less time separated, than couples in which husbands received individual-based treatment only. Husbands in the BCT condition also reported fewer days of drug use, longer periods of abstinence, fewer drug-related arrests, and fewer drug-related hospitalizations through the 12-month follow-up period than husbands receiving individual-based treatment only. However, some of the drug use and relationship adjustment differences between these groups dissipated over the course of the follow-up period.