['To investigate the factors associated with mental health service use among young children.', 'Five hundred ten preschool children aged 2 through 5 years were enrolled through 68 primary care physicians, with 388 (76% of the original sample) participating in a second wave of data collection, 12 to 40 months later. Consensus DSM-III-R diagnoses were assigned using best-estimate procedures. The test battery included the Child Behavior Checklist, a developmental evaluation, the Rochester Adaptive Behavior Inventory, and a videotaped play session (preschool children) or structured interviews (older children). At wave 2, mothers completed a survey of mental health services their child had received.', 'In logistic regression models, older children, children with a wave 1 DSM-III-R diagnosis, children with more total behavior problems and family conflict, and children receiving a pediatric referral were more likely to receive mental health services. Among children with a DSM-III-R diagnosis, more mental health services were received by children who were older, white, more impaired, experiencing more family conflict, and referred by a pediatrician.'] Do mental health service use among young children receiving pediatric primary care?