Congenital heart disease is a frequent feature of Turner syndrome. Although the most frequent cardiac lesion is coarctation of the aorta, a spectrum of cardiac defects occurs which is limited almost exclusively to defects associated with decreased blood flow through the left heart. We report the results of gross anatomic and microscopic dissection of 12 fetuses aborted between 16 and 26 weeks' gestation, with the classic Turner phenotype of nuchal cystic hygromas, hydrops fetalis, and female genitalia. Eight fetuses showed a consistent constellation of cardiac defects: diminution of the ascending aorta, large pulmonary artery ranging from 1 1/2 to three times the size of the aorta, large patent ductus arteriosus, and juxtaductal coarctation. Another fetus had hypoplastic left heart and aortic atresia. The remaining three fetuses had normal cardiac anatomy. The lymphatic vessels at the base of the great vessels were carefully examined in nine of the fetuses. Although there was no definite correlation between the degree of cardiac pathology and the extent of lymphatic aberrations at the base of the heart at the time of postmortem examination, the high incidence (75%) of left-sided flow defects among these fetuses, all of whom had large hygromas and severe edema, supports the hypothesis that there is a pathogenetic relationship between lymphatic obstruction and congenital heart disease in the 45,X Turner fetus.