- Existing research indicates that increased self-efficacy to sustain abstinence is a strong causal mechanism explaining later reduction of drinking. Little is known about how mechanisms of change may differ among distinct subgroups of alcoholics. The purpose of this study was to evaluate the mediational role of self-efficacy on changes in drinking associated with Alcoholics Anonymous (AA) attendance in Type-A and Type-B alcoholics.Analysis of covariance and structural equation modeling were used to model 6-, 9-, 12-, and 15-month data from Project MATCH (Matching Alcoholism Treatments to Client Heterogeneity) participants who were classified as Type-A or Type-B alcoholics (N=1,284; 72% male). Measures of AA attendance and percent days abstinent were taken from the Form 90. Self- efficacy was assessed with the Alcohol Abstinence Self-Efficacy Scale.Alcoholism typology and AA attendance were independent predictors of later self-efficacy, but there was no interaction between typology and AA attendance. Abstinence self-efficacy mediated a modest proportion of the effect of posttreatment AA attendance on later abstinence in both Type-A and Type-B alcoholics. The strength of this mediation did not differ by typology.Self-efficacy for abstinence has a strong direct relationship to abstinence across treatment conditions and typologies. Increases in self-efficacy mediate some of the beneficial effects of AA for Type-A and Type-B alcoholics. Further work is necessary to determine whether self-efficacy plays a different role in the recovery of Type-A versus Type-B alcoholics.