In order to assess the influence of an inherited blood coagulation disorder in individuals who developed cancer, a mail survey of physicians who care for individuals with a bleeding diathesis was evaluated. Sixty-one individuals in an estimated population of 10,500 with both disorders were identified. An apparent increase in the incidence of cancer in the genitourinary and musculoskeletal systems was noted. However, in the largest group ( hemophilia) the primary site of cancer was similar to an age and sex matched population. There did not appear to be a change in the onset of metastatic disease in these individuals, as compared to an individual with cancer who did not have an inherited blood coagulation disorder.