Hemophilia is caused by wide spectrum of different mutations in the F8C gene which made the direct DNA diagnosis of the diseases not the case of choice. Indirect DNA diagnosis by means of linked restriction fragment length polymorphisms (RFLPs) provides the alternative. Using this method authors identified de novo mutation in a family requiring prenatal diagnosis of hemophilia A. This de novo mutation arose during the spermatogenesis of the proband's father. Attempts to characterize the mutation on the molecular level are presented. (Ref. 15, Fig. 1.).