Patients with osteonecrosis who undergo total hip replacement experience an overall failure rate four times greater than that of patients with osteoarthritis who undergo the procedure. Different etiologic factors associated with osteonecrosis appear to carry different prognoses for the durability of total hip replacements. In addition to discouraging total hip replacement in patients under 30 to 40 years of age and making all possible efforts at reduction of the patient's weight and activity, improvement of bone quality, surgical and cementing techniques, prosthetic design, and materials will prolong the durability of total hip replacement. Despite the inferior long-term results of total hip replacement performed for advanced osteonecrosis, we believe the procedure should not be abandoned for patients in their fifth decade or older because it provides a painless, functional hip more consistently than any other form of arthroplasty. These patients should be informed about the importance of protecting the hip replacement by avoiding strenuous activities, impact, and obesity and about the possibilities of future mechanical failure, requiring revision surgery.