We compared direct costs of treatment of Pervasive Developmental Disorder (PDD), asthma, and diabetes in children aged 3-17 years. A retrospective, claims-based study was conducted using the California Medicaid (Medi-Cal) database (1996-2002). Seven hundred and thirty-one children with PDD were identified and matched for sex with an equal number of randomly selected children with asthma and diabetes. Mean total health care costs for PDD were two- to threefold higher than for asthma and diabetes post-diagnosis ($4,815 vs. $1,469 vs. $2,404, respectively, P < 0.0001). Children with PDD incur significantly greater health care costs when compared with children with other chronic pediatric diseases.