To determine the current risk of pediatric cardiac catheterization, the complications and incidents of all catheterizations performed in a pediatric laboratory between January 1986 and October 1988 were prospectively recorded and compared with results from a 1974 study from the same institution. In the current study 1.037 catheterizations, 885 diagnostic and 152 diagnostic/interventional procedures, were performed in 888 patients (aged 1 day to 27 years, median 15.6 months). There were 15 major complications (1.4%), 70 minor complications (6.8%) and 30 incidents (2.9%). Two patients died as a result of the procedure and two as a result of pericatheterization clinical deterioration caused by the cardiac abnormality. The great majority of complications were successfully treated or were self-limited and the patients had no residua. Of patients with 13 nonfatal major complications and 70 minor complications, residua were evident in 7 patients and 3 without evident residua had the potential for sequelae (0.7% and 0.3% of catheterizations). A comparison of the diagnostic and balloon atrial septostomy cases in the present study with similar cases in the 1974 study shows that the incidence of major complications has decreased from 2.9% to 0.9% (p < 0.0001); minor complications and incidents have decreased from 11.7% to 7.9% (p < 0.006%) and pericatheterization deaths not attributable to catheterization have decreased from 2.8% to 0.2% (p < 0.0001). Changes in pericatheterization medical management, patient selection for catheterization and catheterization techniques probably account for these improvements.