The suitability of the Childhood Autism Rating Scale (CARS) for diagnosing adolescents and adults with autism was tested and CARS ratings over time were examined to assess how the characteristics of autism change during adolescence. Subjects (N = 89) had been rated with the CARS before age 10 and again after age 13. A cutoff score of 27 was used; of 59 diagnosed as autistic prior to age 10, 92% were diagnosed as autistic after age 13. Moreover, 9 CARS categories showed significant improvements over time; only 1 showed a significant decrement. The CARS is thought to be a useful screening device for adolescents and adults with autism. Implications of this research for the understanding of autism and how it changes with development are discussed.