Persons with serious mental illness require natural as well as professional supports to maintain successful community integration. Assertive community treatment programs have become preferred treatment modalities nationally for working with such clients, but their potential for developing natural social support resources has not been examined adequately. In this project, two types of community treatment teams were studied, one featuring the extensive use of group treatment modalities and the other using individual client/case manager interventions, with regard to social support outcomes for clients. Through the use of an ex post facto design and analysis of covariance statistics, it was found that the group treatment sample had developed larger personal support networks. There were no differences between groups in the other three dependent variables including range of social network cluster involvements and levels of perceived friend and family support. The group treatment sample also reported more personal contacts in four network clusters. There were gender differences in network size for the entire sample with males reporting larger support networks than females.