The aim of this study was to determine whether a socially focused treatment can effect change in the patient's social network from one that reinforces drinking to one that reinforces sobriety. Alcohol dependent men and women (N = 210) recruited from the community were randomly assigned to 1 of 3 outpatient treatment conditions: network support (NS), network support + contingency management (NS + CM), or case management (CaseM; a control condition). Analysis of drinking rates for 186 participants at 15 months indicated a significant interaction effect of Treatment x Time, with both NS conditions yielding better outcomes than the CaseM condition. Analyses of social network variables at posttreatment indicated that the NS conditions did not reduce social support for drinking relative to the CaseM condition but did increase behavioral and attitudinal support for abstinence as well as Alcoholics Anonymous (AA) involvement. Both the NS variables and AA involvement variables were significantly correlated with drinking outcomes. These findings indicate that drinkers' social networks can be changed by a treatment that is specifically designed to do so, and that these changes contribute to improved drinking outcomes.