We examined theory of mind abilities of individuals with autism, mental retardation (MR) of unknown etiology, Down syndrome, and normal children. On false belief and deception tasks, normal children performed better than all clinical groups, while no differences emerged among the clinical groups. The groups with MR performed better than the group with autism on the value task only. For individuals with autism, theory of mind abilities correlated with verbal ability. For individuals with MR nonverbal abilities correlated with deception and false belief scores. Findings are discussed in terms of the specificity of the theory of mind deficit to autism.