Intervention: A 2-level heart disease screening program was undertaken. Level 1 screening included a history questionnaire and phonocardiography and electrocardiography. Level 2 screening consisted of examination by a pediatric cardiologist of all children who had abnormal findings on level 1 screening. A control group comprised children whose level 1 screening results were normal. Children with abnormalities on level 2 screening were referred for a detailed cardiac evaluation. Main Outcome Measures: Previously unsuspected heart diseases. Results: Of 25 816 children undergoing the level 1 screening program, 5330 had positive findings, of whom 5235 underwent level 2 screening, along with 1104 children in the control group. The pediatric cardiologist referred 780 children to the hospital for full evaluation, including 18 controls and 114 patients with a previous diagnosis of heart disease. A total of 292 children, including 2 controls, had evidence of heart disease, which was previously unsuspected in 178 (61.0%). Excluding children with a previous diagnosis of heart disease, the sensitivity of the screening program was 82.6%. The specificity and the positive predictive value were 98.3% and 28.6%, respectively. Conclusion: The 2-level heart disease screening program has good sensitivity and detects asymptomatic but potentially life-threatening heart disease in some children.