Selected results from the Ontario Child Health Study (OCHS), a cross-sectional community survey of Ontario children four to 16 years of age, are presented in the areas of prevalence, risk indicators and service utilization. The six month prevalence of one or more of four psychiatric disorders (conduct disorder, hyperactivity, emotional disorder, and somatization), in children four to 16 years of age, in Ontario was 18.1%. The highest rate was in 12 to 16 year old girls, and the lowest rate in four to 11 year old girls. Co-morbidity among these four disorders was high while the proportion of disorders identified by more than one respondent was low. Psychiatric disorders co-occurred significantly with other morbidities in children, including poor school performance, chronic health problems, substance use and suicidal behaviour. Chronic medical illness in the child as well as single parent status, living in a family on social assistance and residing in subsidized housing, were all strong indicators of increased rates of psychiatric disorders in children. Specialized mental health/social services, over a six month period, reached fewer than one of five children with psychiatric disorders, as measured in the study. In contrast, ambulatory medical care (primarily visits to family doctors and pediatricians) served almost 60% of Ontario children four to 16 years old, over the same six month period. The results are compared with those in the literature.