The medical history of hemolytic disease of the newborn (h. d. n.) due to Rh is reviewed from 1928-1963 and a very common and widespread error in the international literature on statistical data of h. d. n. has been critically analysed and corrected on the basis of the Viennese material over a period of 25 years. It is shown the first time that the morbidity is not as high as 6 to 7 in 1000 newborns but approximately 3 to 4 taking into account the origin of their mothers. The frequency of h. d. n. in Vienna is strongly influenced by mothers who come from abroad with and without foreign citizenship. In 13,34% of h. d. n. the women produce Rh antibodies during pregnancy, and therefore the Rh prophylaxis given after birth is not able to prevent the immunization which means that 0,55 per thousand of the h. d. n. rate of 4,1 per thousand is caused by Rh antibodies developed intra graviditatem and 3,55 per thousand post partum. These figures are derived from observations between 1948 and 1971 in the Pre-Prophylaxis-Time. The success of the Anti-D-IgG application dropped the h. d. n. rate from 4,1 per thousand to 1,7 per thousand in 1981. If the figure of 0,55 per thousand is taken into account as a wrong "failure" of the post partum prophylaxis, 1,15 per thousand (1,7-0,55) of h. d. n. have to be noted as true failures. There are many causes possible for the high rate of failure in the post partum prophylaxis which is to be eliminated before one could think of a systematic ante partum Rh prophylaxis. In our population 17% are Rh negative, 10% of all mothers are Rh negative giving birth to a Rh positive child and 3,5 per thousand of mothers of h. d. n. develop Rh antibodies post partum, 0,55 per thousand before. Out of 1000 Anti-D-IgG injections given after birth 965 are without any consequence and therefore only 35 are effective. Making use of the ante partum prophylaxis (mother Rh negative, baby's Rh factor unknown) 17% of all pregnant women have to be treated for prevention of only 0,55 per thousand h. d. n. and only 3 injections of 1000 Anti-D-doses are of preventive value whereas 997 are useless.