Eighty-three women with acute icteric hepatitis during pregnancy were followed for evidence of viral transmission to their infants. Six women had acute hepatitis A as diagnosed by appearance of anti-HAV during convalescence. Except for passively acquired antibodies which were present at birth, anti-HAV did not appear in these infants, and there was no clinical or biochemical evidence for hepatitis during follow-up. Sixty-five pregnant women had acute hepatitis B during pregnancy or in the immediate postpartum period. Transmission to infants often occurred when both maternal HBsAg and HBeAg were positive at delivery of postpartum. A majority of these infants never developed jaundice, have remained persistently HBsAg-positive, and have had periodic serum ALT elevations during follow-up. Twelve women had acute non-A, non-B hepatitis during pregnancy. Infants born to 6 of these women near term had transient elevations of serum ALT values at 4-8 wk of age, suggesting maternal transmissibility of the non-A, non-B viral agent.