Substance abusers in treatment have cigarette-smoking rates about three times that found in the general adult population, yet there is a paucity of published studies examining smoking-cessation programs for these clients. Accordingly, a behaviorally based smoking-cessation program for methadone maintenance clients was developed, and the efficacy of a methadone dose increase as a pharmacological adjunct was tested in a double-blind placebo-controlled study. While no significant difference between experimental and control subjects in reported abstinence rates was found, subjects receiving a methadone increase reported significantly more nicotine craving and other withdrawal symptoms during the first week of abstinence than did controls. Measures of smoking rates indicated that experimental subjects smoked significantly more than controls throughout the 10-week study period. Although the initial smoking abstinence rate of 65% was encouraging, most subjects returned to smoking by the end of the study period. These findings indicate that the development of smoking-cessation programs for methadone clients merits further study and that such programs should stress relapse prevention techniques tailored to the specific needs of this population. Also, while the use of a methadone dose increase as a pharmacological adjunct has not been found to be efficacious, other pharmacological strategies involving the use of nicotine should not be ruled out.