This study explored cultural differences on the behavioral symptoms of autism among African Americans in the United States and Kenyan school-aged children and adolescents with autism. To accomplish this goal, the Gilliam Autism Rating Scale (GARS) and the Autism Behavior Checklist (ABC) were used. In addition, a Developmental History Questionnaire (DHQ) was designed specifically for this study. Eighty individuals (40 African Americans and 40 Kenyans) were matched for age and gender. To control for perceptual differences between African American and Kenyan raters, 20 typically developing children, 10 from each culture, served as a comparison group. Multivariate analysis and independent t tests revealed significant differences on social interactions, communication, stereotyped behaviors, developmental disturbances, and overall behavior disturbances between Kenyan individuals and African Americans with autism. There was a clear trend that Kenyans with autism showed more problems on all behavioral symptoms of autism than their U.S. counterparts. The individuals with autism were divided into four age groups. At age 3–7, Kenyans with autism showed fewer problems on sensory subscale of the ABC. At 8–12, Kenyans showed fewer problems on social interaction of the GARS. An interesting finding was that at age 13–17, behavioral symptoms were fewer for both groups but increased at age 18–21 for both groups. Overall, the behavioral symptoms of autism increased by age for Kenyans group and decreased with age for African Americans. There were no significant differences between normal individuals in Kenya and the United States on any of the symptoms. Therefore, differences between the two groups appear to be actual differences in the behavioral symptoms of autism and not a reflection of raters’ perceptual differences in Kenya and the United States.