Research on the prevalence, characteristics, and treatment of obesity of mentally retarded individuals within the context of research findings with the obese nonretarded population was selectively reviewed. According to the available literature, obesity is a prevalent problem in the retarded population, and there is a greater incidence among females than males. The literature also suggests that obese retarded subjects as a group can be distinguished from their nonobese peers by their physical condition, but not by their eating style or personality characteristics. Behavioral self-control strategies have been found to be effective in producing weight loss in obese retarded children and adults. Further research is needed to reduce the high interindividual variability observed in treatment outcome studies and to address problems of long-term maintenance of weight loss.