This longitudinal study investigated developmental change in theory of mind among 57 children with autism aged between 4 to 14 years at the start of the study. On an initial visit and one year later, each participant was administered a battery of tests designed to measure a broad developmental range of theory of mind abilities from early (e.g., desire) to more advanced (e.g., moral judgment) mental state understanding. Both group and individual data indicated significant developmental improvement in theory of mind ability, which was primarily related to the children's language abilities.