Introduction: Brief episodes of ischemia followed by periods of reperfusion generate a powerful protective mechanism in cell, tissue or organ, which increase the resistance to further ischemic damage. This is known as ischemic preconditioning, and has not been investigated in testis. The present experiments were undertaken to determine whether early phase of ischemic preconditioning is evident in rat testis. Materials and Methods: Surgery was conducted under thiopental ( 60 mg/kg, intraperitoneal) anesthesia in male Wistar rats. Surgical procedures were performed through a midline incision. Group 1 was designed as a sham group. In group 2, which served as the ischemia group, the animals were subjected to unilateral testicular torsion by rotating the left testis 720degrees in a clockwise direction. Then, this testis was maintained in the torsion position by fixing with a silk suture to the scrotal wall for 90 min. In groups 3 and 4, 5 or 10 min ischemia followed by 10 min reperfusion was introduced, respectively, to induce single cycle ischemic preconditioning. In group 5, which served as the multiple cycle preconditioning group, 3 cycles of 10 min ischemia and 10 min reperfusion were applied prior to 90 min ischemia. Both ipsilateral and contralateral testes were removed from the rats at the end of the experimental periods, and tissue malondialdehyde (MDA), nitric oxide ( NO) levels, xanthine oxidase (XO), myeloperoxidase (MPO) and superoxide dismutase ( SOD) activities were measured. Both testes were also evaluated histologically, assessing interstitial edema, congestion, hemorrhages, rupture of tubules and Leydig cell proliferation. Results: 90 min ischemia produced a marked increase in MDA level in left testis. However, all ischemic preconditioning protocols used in this study did not show any significant modification in MDA, NO levels or XO, MPO and SOD activities. Histological grading scale was also similar in ischemia and preconditioning groups. Conclusion: These results suggest that there are no protective effects with ischemic preconditioning in rat testis as showed by biochemical analysis and histological examinations. Copyright (C) 2005 S. Karger AG, Basel.