We have had occasion to observe the occurrence of multiple myeloma in two siblings. These patients were not twins. We are unaware of any previous report of this disease occurring in siblings. None of the approximately 550 patients suffering with multiple myeloma seen in the past at the Mayo Clinic1 were siblings. The criteria for the diagnosis of multiple myeloma are well established and need not be repeated here. The value of urethan (ethyl carbamate) in the treatment of some cases of multiple myeloma has been reported by a number of investigators. Kenny and Moloney2 reported the long-term use of urethan in three cases of multiple myeloma. Two of their patients were alive and well 11 years after administration of the drug was begun, and the third patient was alive 9 years after he first received urethan. These investigators emphasized that in all three cases the myeloma cells