The present study pursued hypotheses relevant to prosodic abnormalities in the expressive language of autistic children. An operant paradigm was employed to measure the intrinsic reinforcing value of a verbally presented story for autistic, mentally retarded, and normal groups controlling for chronological age and performance mental age. Results suggested that both autistic and mentally retarded children could perceive prosodic cues, although only mentally retarded children are able to use them in their expressive language. It was also suggested that linguistic stimuli may have less intrinsic reinforcement value for autistic and mentally retarded children than for normal children. Implications for future research and treatment were discussed.