Treatment of coagulation deficiencies with high dosages of the missing factor is a source of continuous diffusion of homologous proteins that could modify the normal immunological profile. We have performed immunologic studies on 24 children with ages ranging from 1 - 16 years with severe classical hemophilia and 1 child with von Willebrand's and on a control of 19 age-matched healthy children. Our preliminary data show no statistically significant alterations in the basic immunological profile between normal children and those with hemophilia. Nor were there any differences among the hemophilic patients on the various transfusional regimes. Considerations are made on the reasons for the discrepancies between our results and those on adults presented in the literature.