One hundred forty-four pregnancies that occurred in 74 patients with congenital heart disease at the Toronto General Hospital between 1975 and 1986 were reviewed. The patients were divided into two groups, those with acyanotic lesions and those with cyanotic lesions. Maternal and fetal outcomes in these two groups were compared. Patients with cyanotic lesions developed significantly more congestive heart failure and deteriorated more often in functional cardiac status than those with acyanotic lesions (p less than 0.005). Women with obstructive lesions had a higher incidence of pregnancy-induced hypertension than our general population (p less than 0.005). There was one maternal death in the puerperium in a woman with Eisenmenger's syndrome. Preterm births were more frequent in the cyanotic group (p less than 0.01) as were small for gestational age infants (p less than 0.005). In the cyanotic group the mean birth weight was 900 gm less than that in the acyanotic group (p less than 0.005). The major benefits of corrective cardiac surgery were in the cyanotic group and consisted of fewer spontaneous abortions (p less than 0.01) and small for gestational age infants (p less than 0.02) and more term births (p less than 0.01). Long-term follow-up revealed that 19.2% of women with acyanotic lesions had significant cardiac developments, compared with 90% in the cyanotic group (p less than 0.005). One of 87 infants (1.1%) had congenital heart disease and two had Marfan's syndrome.