This study examined lifetime medical and psychiatric morbidity reported by caregivers of 2917 autistic adults participating in the US research cohort SPARK. Participants were 78.4% male, 47.3% had intellectual disability, and 32.1% had persistent language impairments. Childhood language disorders (59.7%), speech/articulation problems (32.8%), sleep (39.4%) and eating problems (29.4%), motor delays (22.8%) and history of seizure (15.5%) were the most frequently reported clinical features. Over two thirds (67.2%) had been diagnosed with at least one psychiatric disorder (anxiety disorders: 41.1%; ADHD: 38.7%). Compared to verbally fluent participants, those with language impairments had lower frequencies of almost all psychiatric disorders. Female sex and older age were associated with higher medical and psychiatric morbidity. [This article was written with the SPARK Consortium.]