Many alcohol treatment programs have stressed a sense of belongingness as a means for successful treatment of alcoholics in a residential setting. An examination of the effectiveness of this strategy in highly structured and less structured programs involved 200 chronic, recidivistic male adult alcoholics in a residential program. Subjects were randomly assigned to either a highly structured or a less structured version of the same program. Data from pre- and posttest structured interviews were used to classify clients' belongingness type (isolate, dyad, cluster, variant). Treatment outcome was measured by length of stay in the program and rate of relapse. The findings indicated no significant relationship between program structure and belongingness level change. There was a significant relationship between belongingness posttest level and length of stay, and between belongingness posttest level and relapse rate. Program structure was found to have a significant relationship to length of stay but not to relapse rate. These results support the importance of a high level of client belongingness to successful treatment outcome. However, the results indicate that the highly structured program format should be questioned as to whether or not it is the most effective strategy for achieving desired results. (NRB)