Three hundred twenty-nine parents of developmentally disabled children (0 to 21 years old) were surveyed to test the hypothesis that parents who join parent groups are more likely to be white, highly educated, currently married, Republican, and to have higher family incomes than those who do not join parent groups. The survey questionnaire was designed to provide data regarding: the manner in which the parents first discovered their child was developmentally disabled; availablity of extended family and community support networks; the severity of the disability; the manner in which parents secure community services; professionals utilized; attitudes regarding direct services; involvement in children's educational programs and parents' organizations; opinions about public policy; and long term plans and objectives for their children. Findings were grouped according to characteristics of parents and their children, activities of parent group members and reasons for not attending parent group meetings, and differentiating characteristics of group members and nonmembers. Among findings were the following: although the questionnaires were mailed to both parents in two parent families, almost all were completed by mothers; out of a list of seven reasons commonly given for nonattendance at parent groups, the logistical problem of arranging for babysitters or transportation was reported as a barrier far more often than negative feelings about aspects of the meetings themselves; of those parents who identified themselves as group members, their greatest area of group activity was in the core element of a self help group, socializing with new parents; and parents of preschool age children were most likely to have attended more than four meetings per year while parents of 18 to 21 year old children were least likely. In comparing group members with nonmembers, group members tended to be wealthier and older, their children had lower cognitive skills, they relied on the personal support network more often by seeking friend's advice, they confided in professionals more often, and were higher utilizers of speech therapist services. A detailed explanation of variables is appended. (SW)