The genetic familial register in question contains information on 441 hemophilia patients. Two-thirds of the patients suffered from moderate or severe hemophilia, 81.3% had hemophilia A. Fifty-two families with the latter disease were examined with molecular methods which confirmed heterozygous carriage in 40% of the female examinees. The prenatal diagnosis in two families led to delivery of healthy boys. The genetic register provides effective protection for hemophiliac families.