A young woman had idiopathic autoimmune hemolytic anemia occurring in the last weeks of pregnancy. The hemolytic process was quite severe in the mother but responded to steroid therapy and transfusions. The baby was born with a mild form of hemolytic disease with elevated indirect bilirubin levels, increased normoblasts and reticulocytes, and a positive direct antiglobulin test. The child did not require any exchange transfusions, and although the hemoglobin fell to a low of 9.7 g/100 ml 1 mo after delivery, it continued to rise to normal levels after that. The child is developing normally. The antibody was an IgG globulin, presumably 7S, and crossed the placenta to react with the fetal red cells. The antibody showed no specificity when tested with a panel of cells, including Rh null cells.