The authors retrospectively reviewed 53 hip replacements performed in 50 patients (mean age, 65 years) for plasmacytoma (four lesions) or multiple myeloma (49 lesions) of the hip region. Perioperatively, 49 patients received chemotherapy. Twenty-four hip lesions had radiation therapy. Within a mean followup period of 32.6 months, 15 (28%) complications occurred. Late deep infection, dislocation, and aseptic loosening with medial migration of the acetabular component occurred in one patient each. Three patients died during the first postoperatively month. All of the remaining patients postoperatively regained their previous ambulatory status; hip pain relief was achieved in 98% of patients. At the time of the latest followup evaluation, 84% of the patients had died (median survival time, 18 months) and 16% were still alive (median survival time, 76 months). Patients with plasmacytoma had longer survival than did patients with multiple myeloma (median survival, 6.3 years versus 18 months, respectively). No significant association was found between patient survival and the stage of disease at diagnosis, age, gender, type or location of the myeloma lesion, or the type of implant used. Because of the relatively long survival time, prosthetic replacement is indicated for extensive hip lesions in patients with plasmacytoma or multiple myeloma.