A number of studies have reported that most children with autism fail theory of mind tasks. It is unclear why certain children with autism pass such tests and what might be different about these subjects. In the present study, the role of age and verbal ability in theory of mind task performance was explored. Data were pooled from 70 autistic, 34 mentally handicapped, and 70 normal young subjects, previously tested for a number of different studies. The analysis suggested that children with autism required far higher verbal mental age to pass false belief tasks than did other subjects. While normally developing children had a 50% probability of passing both tasks at the verbal mental age of 4 years, autistic subjects took more than twice as long to reach this probability of success (at the advanced verbal mental age of 9-2). Possible causal relations between verbal ability and the ability to represent mental states are discussed.