Forty-two unstable, four-part intertrochanteric fractures in forty-one patients (seventy-one to 104 years old) with severe osteoporosis were treated by open reduction and internal fixation (Jewett nail or compression screw-plate) supplemented with methylmethacrylate packed into the curetted medullary space. One patient was lost to follow-up, one died of a myocardial infarction at six weeks, and one was excluded because of an unsuspected myeloma found at the fracture site. All patients were sitting up in a chair the day after operation. Full weight-bearing on the limb was started within three weeks by thirty patients and at an average of 118 days by six who had very comminuted fractures. Three patients, non-ambulatory preoperatively, did not walk after operation. Of the thirty-eight fractures followed for from nine to thirty-seven months, thirty-seven healed with no loss of position. One fracture which had been fixed with the nail and cement not extending far enough into the head and neck displaced, and the operation had to be repeated, this time with a successful result. The fractures healed by periosteal new-bone formation. There was no evidence of avascular necrosis or wound complications.