The number of Rh-D sensibilizations provided by pregnancy and delivery has decreased as the result of the preventive measures introduced to the combat this condition. The problem, however, still exists, and to cope with it, the determination of the blood group, Rh-D factor, and the Coombs' test using the amnionic fluid allows a timely preparation for the therapy of the newborn's hemolytic disease. The method of the neutralization technique employed by the authors has proved reliable.