176 men scheduled for primary total hip or knee arthroplasty were randomized to begin a course of either tamsulosin 0.4mg or placebo daily five days prior to surgery, and continue until the first postoperative day. Patients were assessed for the development of postoperative urinary retention postoperatively. The purpose of this study was to determine if prophylactic tamsulosin reduced the incidence of postoperative urinary retention. Results demonstrated no significant difference between the tamsulosin group and the placebo group for the incidence of developed of postoperative urinary retention.