The gratifying advances in the surgical therapy of congenital cardiovascular anomalies have resulted in an intensified interest in patients with these defects and increased the importance of early detection and accuracy of diagnosis. Cardiac catheterization, angiocardiography, aortography, cardiac roentgenology and the electrocardiogram are indispensable for accurate diagnosis The electrocardiogram is the most readily obtainable of these tests. It may be of considerable aid in the evaluation of patients who have or are suspected of having a congenital cardiovascular anomaly.We have reviewed the electrocardiograms of patients with proved congenital cardiovascular defects seen at the State University of Iowa Hospitals over the past 10 years in an effort to correlate electrocardiographic abnormalities with the several defects. The study has been limited to patients with the anomalies currently most amenable to surgical therapy: coarctation of the aorta, patent ductus arteriosus, ventricular septal defect, atrial septal defect, isolated pulmonic stenosis, and tetralogy of Fallot. Diagnoses were established at operation, or by autopsy, cardiac catheterization or aortography. Table 1 lists the total number of patients in each category. METHODS All electrocardiograms were recorded on a standard single channel electrocardiograph at a paper speed of 25 mm/sec. The usual standard, unipolar limb and precordial leads were obtained. In most instances additional precordial leads, V3R , V4R , Hvi , Hv2 and V7 were available for analysis. Each tracing was interpreted independently by three observers. The criteria of Dyers' as outlined in table 2 were used for the interpretation of atrial abnormality, right (RVH) and left (LVH) ventricular hypertrophy, incomplete right bundle branch block (IRBBB) with or w ithout RVH, and complete right bundle branch block (RBBB).The criteria for an rSR' type of RVH, IRBBB and IRBBB with RVH are graphically shown in figure 1. Normal variations for the P-R interval. in children were judged by the standards of Alimurung and Massell.1It is emphasized at the outset that we have applied the Dyers' criteria rigidly in the belief that an attempted correlation otherwise would TABLE 1 TABLE 2