Semen parameters from 4 patients with testicular injury after uniorchiectomy were investigated. Semen volume and sperm morphology were not affected after the operation, but sperm count and motility were severely diminished. Two of 4 cases showed azoospermia, and the other 2 cases showed low values in both sperm count and motility. After 150-300 days from the operation, 2 cases recovered to the normal range in sperm count while the other 2 remained in the abnormal range. In sperm motility, 3 cases recovered to the normal range but the rest remained abnormal. The results suggest that long-term follow-up in semen parameters is needed when unilaterial orchiectomy is performed.