Percutaneous injection of methylmethacrylate or ethanol may provide marked pain relief or bone strengthening in patients with malignant acetabular osteolyses who are unable to tolerate surgery. Injection of methylmethacrylate is usually indicated when osteolysis involves the weight-bearing part of the acetabulum (ie, the acetabular roof); in all other cases, ethanol injection is preferred. Ethanol and methylmethacrylate injections may be performed together if both weight-bearing and nonweight-bearing parts of the acetabulum are involved or extensive soft-tissue involvement is present. Moreover, these injections may be performed prior to radiation therapy, which complements their action due to similar but delayed effects on pain, or after radiation therapy that failed to relieve pain or in cases of local recurrence. Radiography and computed tomography must be performed prior to therapeutic percutaneous injection to assess the location and extent of the lytic process, the presence of cortical destruction or fracture, and the presence of soft-tissue involvement. Fever and transitory worsening in pain may occur secondary to inflammatory reaction in the hours following injection; however, these side effects usually resolve spontaneously within 1-3 days. The decision to perform therapeutic percutaneous injections should be made by a multidisciplinary team because the choice between this option and alternative methods of treatment depends on several factors including the location of the lesion, the local and general extent of the disease, the pain and functional disability experienced by the patient, and the patient's state of health and life expectancy.