A regional case-control study of congenital cardiovascular malformations (CCVMs) searches for all live-born infants in the community in whom the cardiac diagnosis has been confirmed by echocardiography, cardiac catheterization, surgery, or autopsy. Their families are studied in comparison to those of a representative sample of resident live-born infants. Detailed descriptions of noncardiac abnormalities are obtained from physician reports and maternal interviews expanded by medical record and death certificate data. Among 1,494 cases and 1,572 controls, chromosomal abnormalities, syndromes, heritable disorders, and suspect syndromes occurred with an overwhelming excess in cases (chromosomes, P less than 10(-4); syndromes/heritable disorders, P less than .005). Abnormalities affecting chromosomes 13, 18, and 21 constituted 93% of the cytogenetic defects. Syndromes and heritable disorders were of 39 types. Nonsyndromic abnormalities were three times more frequent in cases than in controls (P less than .005). Case excesses occurred for central nervous system malformations, eye disorders, major abdominal wall defects, and abnormalities of the alimentary and urinary tracts. Severe anomalies frequent among cases were those which also occur in certain recognized syndromes, and it is suggested that paired combinations of cardiac and other midline anomalies may represent "formes frustes" of syndromes with similar though variable phenotypic expressions. Cleft lip and palate, inguinal hernia, and lower limb anomalies occurred with equal frequency, suggesting their association with CCVMs by chance alone.