We identified correlates of participation in a breast cancer support group.  Thirty-eight breast cancer patients were classified as established members, new members, or nonmembers of breast cancer support groups and were administered a Background Data Sheet, Medical Questionnaire, and the Personality Assessment Inventory.  Established members were most educated, had the most friends with cancer, perceived group as more supportive than new members, and identified coping skills and sense of community as the most helpful features of group; new members held longer meetings than established members, rated their relatives as least supportive, and cited medical information as the most beneficial feature of group.  Established members manifested the least anxiety, depression, stress, nonsupport, and aggression. We integrate these findings with the literature on social support an cancer and offer suggestions for research and practice.