To collect and analyze data on females with hemophilia so as to better define the difference between the study population and the male population with hemophilia.

This study is designed as an epidemiological study with retrospective clinical and genetic data collection and prospective quality of life (QOL) data collections and genotyping of subjects without current molecular diagnosis. Data on the genetic/chromosomal etiology of the condition will be collected through chart review. For those subjects who have not had molecular or cytogenetic analysis, molecular and cytogenetic testing will be offered after genetic counseling. Those subjects who agree to have genetic testing will have 5-10 ml of blood drawn and sent to the cytogenetic laboratory at Weill Cornell Medical College for testing to determine the chromosomal complement, and 5 ml of blood sent to Dr. Arupa Ganguly at the University of Pennsylvania for the identification of a factor VIII or factor IX mutation, and X-chromosome inactivation studies.

Inclusion Criteria:

• Females with severe (FVIII<0.01u/dl) or moderate (FVIII-0.01<0.06 u/dl) hemophilia A
• Females with severe (FIX<0.01u/dl) or moderate (FIX-0.01<0.06u/dl) hemophilia B
• Willingness to participate in the study.

Exclusion Criteria:

• Subjects who do not meet the inclusion criteria with respect to gender or hemophilia severity.

Females with severe or moderate (less than 5%) hemophilia A or B.