This study was designed to investigate the effect of selenium on ipsilateral and contralateral testicular damage after unilateral testicular torsion/detorsion (T/D). Thirty-two male rats were divided into four groups, each containing eight rats. Torsion was created by rotating the right testis 720 degrees in a clockwise direction. Group 1 underwent sham operation to determine basal values for biochemical and histopathological evaluation. Sham operation was performed in group 2, and sodium selenate (0.2 mg/kg) was given intraperitoneally. Group 3 served as a T/D group, receiving 4-h torsion and 4-h detorsion. Similarly, in group 4 sodium selenate (0.2 mg/kg) was injected intraperitoneally 20 min before detorsion. Bilateral orchiectomies were performed for measurement of tissue malondialdehyde (MDA) levels and superoxide dismutase (SOD) activities and histopathologic examination. The results were compared statistically. The highest MDA and the lowest SOD values were determined in both testes in group 3. There were statistically significant differences in MDA levels and SOD activities in group 3 compared with group 4. Specimens from group 3 had a significantly greater histologic injury than other groups. These results suggest that ischemia-reperfusion injury occurred in both testes after unilateral testicular T/D and that selenium administration before detorsion prevents reperfusion injury in testicular torsion.