This study tested the efficacy of a new social skills intervention, S ocial S kills GR oup IN tervention-High Functioning Autism (S.S.GRIN-HFA), designed to improve social behaviors in children with high functioning autism spectrum disorders. Fifty-five children were randomly assigned to S.S.GRIN-HFA treatment (n = 27) or control (i.e., traditional S.S.GRIN intervention; n = 28). Examination of the direction and magnitude of change in functioning revealed that children who participated in S.S.GRIN-HFA exhibited significantly greater mastery of social skill concepts compared to children in the control group. Parents of S.S.GRIN-HFA group participants reported an improved sense of social self-efficacy, whereas parents of control participants reported a decline. The advantages of a specialized intervention such as S.S.GRIN-HFA, designed specifically for children with high functioning autism spectrum disorders, are discussed.