Aims. A conceptual clarification of the domain of social relationships defines three aspects of social relationships (structure, function and quality), which have both alcohol-specific and general components. We analyse the correlations among post-treatment indicators of social relationships and the associations between these interpersonal variables and post-treatment drinking and subjective wellbeing. Design. This is a secondary analysis of data from an alcohol treatment outcome study, in which subjects were randomly assigned to one of three treatment conditions and followed for 18 months. Setting. The outpatient treatment program is located within a private psychiatric hospital in the north-eastern United States. Participants. We analyzed the 140 subjects who completed a social network instrument 12 months following treatment assignment. Intervention. This secondary analysis combined clients from three treatment conditions, all of which were based upon social learning theory. Measurements. Interview and questionnaire self-report data were collected by trained interviewers. Findings. Indicators of social relationships are found to be relatively independent of one another. Only alcohol-specific social relationship indicators are significantly associated with drinking outcomes, and only general indicators are significantly associated with subjective wellbeing. Functional indicators, addressing social interaction content, have stronger effects on outcomes than structural or quality indicators. General and alcohol-specific support from friends have more influence than support from family; both surpass the influence of co-workers. Conclusions A better understanding of the roles of social relationships during the course of treatment and recovery or relapse may help clarify how treatment personnel can utilize clients' interpersonal relationships more effectively to maximize treatment effectiveness.