Routine epicardial two-dimensional echocardiography, Doppler, and Doppler color flow imaging studies were performed before and after cardiopulmonary bypass in 328 patients undergoing operations for congenital heart disease. Ages ranged from 1 day to 59 years (mean 5.9 years); the smallest patient was 1.8 kg. Complete examinations were conducted in 3.6 +/- 1.7 minutes. Prebypass examinations demonstrated previously unappreciated details of anatomy in 60 patients (18%), which did not relate to whether catheterization had been performed, and they were believed to play a role in surgical planning in 143 patients (44%). Discovery of previously unrecognized features of anatomy increased the impact of echo-Doppler color flow imaging on operative planning by 2.5 times. After bypass, echo-Doppler color flow imaging disclosed unsuspected residual defects in 22 patients (7%) who were doing well clinically and enabled an attempt at immediate revision of the procedure. When ultimate clinical outcome was compared to postbypass findings of echo-Doppler color flow imaging, the presence of a residual defect, right or left ventricular dysfunction, or any concern with the heart by echo-Doppler color flow imaging appeared to serve as a predictor of unfavorable outcome (p less than 0.001 for each when compared with absence of these difficulties). Thus routine intraoperative echo-Doppler color flow imaging is useful in aiding the planning, conduct, and assessment of results in operations for congenital heart disease.