Analyzing data of 125 multiple myeloma patients, the authors found a 40-fold increased tumor incidence among the patients and their first-degree relatives as compared to the average population. These tumors were the same as those usually found among Hungarians. There was no difference as to the patient's blood group antigens in the families of myeloma patients with or without other tumor. IgA-type disease was found to be relatively more frequent in the group of patients who had tumor besides myeloma. In a prospective study, authors could not find mutation of suppressor gene p53 in 14 patients and their 16 healthy first-degree relatives. This may indicate that there is no p53 suppressor gene alteration responsible for the high-risk condition for tumorgenesis in this population.