This communication is a case report of a 41 year old man with a lesion of the trochanteric region of the right femur. It is of interest from the standpoint of diagnosis and prognosis. Before operation the lesion of the proximal end of the right femur was felt to be a hemorrhagic bone cyst, although the possibilities of a benign or malignant bone tumor were also considered. The pathologic report on the tissue removed at operation was plasma cell myeloma of the trochanteric region of the right femur. Operation consisted of curettage and packing of the cavity with multiple small bone chips removed from the left tibia. Following operation, therapy of 1,500 roentgens was applied to the involved area. Symptoms had begun one year prior to operation. After operation and irradiation the femoral lesion appeared to remain inactive and showed x-ray evidence of progressive repair at the operative site. The