We collected data on 930 neonates with structural congenital heart disease seen during 1975-1977 at the existing pediatric cardiac referral and treatment centers in Ontario. Estimates were made of unmet need for pediatric cardiology services in Ontario. The data showed that a number of counties had significantly low referral rates and that at least 25% of the newborns with severe structural heart disease (that is, 75 newborns each year) were not seen by pediatric cardiologists, although the children would benefit from prompt assessment and rapid treatment under specialist supervision.