This paper investigates the mediational effects of family functioning on the socioemotional adjustment of non-disabled siblings of children with developmental disabilities. Families who participated were placed into two groups, those raising a child with developmental disabilities and those raising a child with typical development, with 28 families per group. Parents and siblings from both groups completed several measurement scales. The results indicated that families of children with and without developmental disabilities showed similar family functioning and siblings showed similar anxieties and scored the same on self concept measures. Family problem solving communication significantly predicted siblings' adjustment, and the presence of a child with a disability in the family significantly predicted lower self concept for siblings of children with developmental disabilities. Findings provide support for programs that facilitate effective family problem solving communication. (Contains 5 tables and 10 references.) (JDM)