This study examined the effects of group social support on the reduction of burden and increase in well-being of mothers of developmentally delayed children. The research used a one group pre-post experimental design. The independent variable in the experiment was group social support. Two series of 4-weekly meetings for group social support were conducted by the researcher with the intention of developing a self-help group. The dependent variables were burden and well-being. Well-being was operationalized as physical symptoms and quality of life. Thirty mothers of developmentally delayed infants from the rehabilitation center of a medical center participated in the study. Data were collected by interview and a self-administered questionnaire. The mean age of the subjects was 29.9 years. Changes of the dependent variables between pre and post tests were compared using the t-test. Even though there was a slight improvement in the scores for the dependent variables, they were not statistically significant. The items, "I resent my baby", "I feel angry about my interactions with my baby", "I feel guilty in my relationship with my baby" showed a significant decrease in burden score and were statistically significant. Symptoms of loneliness, constipation, anxiety, restlessness were less and feeling of happiness was greater after participation in the group social support, than on the pretest. The mothers showed emotional instability and frustrations during the group sessions but their reactions in general were positive. Emotional support, stress management and information provided were identified as the most valuable content of the sessions. However, participation was not active due to the mother's denial, delayed acceptance and/or avoidance of their infants' problems. It can be seen that group social support for the mothers with developmentally delayed children should be provided after infancy when the mothers have time to accept their children's conditions and are ready to receive support. The use of comprehensive instruments which measure burden in both families and mothers needs to be developed for future research.