We investigated if shifts in the coding of qualifying conditions in the California Department of Developmental Services (DDS) have contributed to the increase in California children with autism observed in recent years. Qualifying condition codes for mental retardation (MR) and autism in DDS electronic files were compared to hard-copy records for samples of children born 1987, 1990, 1994, and 1997. Contrary to expectations, we did not find evidence of a coding shift from "MR only" to "both MR and autism" or an increase in the proportion of children with coded autism who lacked supportive diagnostic documentation in records (possible "misclassifications"). These results indicate that changes in DDS coding practices are unlikely to explain the increase in DDS clients with autism.