The study compared play among five groups of children (ages 3-7 years): normal children (N=41); those diagnosed with language delays (N=241), those with autism but normal intelligence (N=71), those with autism and mental retardation (N=97), and those with nonautistic mental deficiency (N=86). Each child was evaluated using a 25 minute structured play session which was videotaped for later analysis. The child's activities were classified into 11 types falling into 5 categories: passive sensory-motor play; active sensory-motor play; functional play; symbolic play; and no toy play. Results indicated that the development of play, especially the later emerging symbolic type, is dependent on cognitive abilities and social comprehension. The children with the most noticeable deficit in symbolic play were the autistic groups, with the deficit more profound in the low IQ group. An unexpected finding was that although language also requires symbolic representation, those children with language impairments did not demonstrate significantly less symbolic play. Members of all groups chose approximately the same number of toys during a typical play session. Includes 5 references. (DB)