Excitement and controversy have surrounded the effectiveness of Early Intensive Behavioral Intervention (EIBI) for young children with autism. The purpose of this meta-analysis was to investigate the effectiveness of EIBI based on applied behavior analysis in young children with Autism Spectrum Disorders (ASD). There were 11 studies with 344 children with ASD. Quality of studies was assessed using the Downs and Black Checklist. Experimental groups who received EIBI outperformed the control groups on IQ, non-verbal IQ, expressive and receptive language and adaptive behavior. Differences between the experimental and control groups were 4.96-15.21 points on standardized tests. These results strongly support the effectiveness of EIBI. (Contains 9 figures and 2 tables.)