The aim of this study was to investigate two questions: Does arthroplastic surgery affect the patient's status as being sexually active; and if patients are sexually active, does surgery affect their erectile function? The study was designed prospectively and the patients filled in a questionnaire concerning sexuality and erectile function before and 6 months after alloplastic hip-or knee surgery. Ninety-nine males were included, mean age 70.6 y. The results demonstrate that 17% of patients lost a sexual activity that they had preoperatively, and no one regained sexual activity after surgery. A correlation between increasing age and risk of losing sexual activity was demonstrated. 26.1% lost a normal erectile function they had preoperatively, while 6.7% regained normal erections. A similar correlation between increasing age and increased risk was demonstrated. From this study of elderly males undergoing orthopaedic alloplastic surgery it is concluded that the risk of losing sexual activity and erectile capability is increased after surgery, and especially in the group where sexual functions are already impaired.