This study extends findings on the effects of intensive applied behavior analytic treatment for children with autism who began treatment at a mean age of 5.5 years. The behavioral treatment group (n = 13, 8 boys) was compared to an eclectic treatment group (n = 12, 11 boys). Assignment to groups was made independently based on the availability of qualified supervisors. Both behavioral and eclectic treatment took place in public kindergartens and elementary schools for typically developing children. At a mean age of 8 years, 2 months, the behavioral treatment group showed larger increases in IQ and adaptive functioning than did the eclectic group. The behavioral treatment group also displayed fewer aberrant behaviors and social problems at follow-up. Results suggest that behavioral treatment was effective for children with autism in the study.