We report the case histories of two patients with histologically confirmed adenocarcinoma of the prostate, both of whom had been treated with steroidal anti-androgen therapy in the form of cyproterone acetate prior to radical or palliative pelvic irradiation, and who subsequently developed femoral head avascular necrosis. This is a diagnosis that should be considered in patients with prostate cancer who present with hip pain in the absence of biochemical evidence of disease progression.