Forty-nine 2 years olds with social and language characteristics suggestive of autism were identified by community professionals and screening tools, then given a diagnostic assessment and reexamined at age 4 1/2. Agreement between autism clinic and screenings was high, with 88% receiving a diagnosis on the autism spectrum. The children were lower functioning relative to the autism population, thus more likely to be identified early. Reliability of diagnoses from 2 1/2 to 4 1/2 was high with 79% staying in the same diagnostic category, but more so for clear autism than for PDDNOS. About a third improved over 20 IQ points and similar number similarly declined. Changes were not related to amount or type of intervention but were related to the children's characteristics. Higher functioning children with milder autism were the most improved.