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.