Introduction: An experimental study was planned to evaluate and compare the effects of orchidopexy and orchidectomy on ipsilateral and contralateral testes in rats subjected to ipsilateral abdominal testis and vas deferens obstruction. Materials and Methods: Four groups of 12 rats each were established. Sham operation, intra-abdominal testis with vas deferens obstruction and orchidopexy or orchidectomy for prior intra-abdominal testis with vas deferens obstruction were performed in groups 1, 2, 3 and 4, respectively. While testes were maintained for 8 weeks in the same position in groups 1 and 2, orchidopexy or orchidectomy was performed in groups 3 and 4 after the first 4 weeks, and the remaining testes were harvested after an additional 4 weeks. Lactic acid hypoxanthine contents were determined and the groups were compared with the paired t test. Results: Maintaining intra-abdominal testis with vas deferens obstruction for 8 weeks and orchidopexy yielded the highest lactate values. However lactate levels in contralateral testes did not increase. On the other hand, hypoxanthine levels revealed the highest values after the initial 4 weeks. The 8-week study period resulted in increases of ipsilateral and contralateral testicular hypoxanthine levels. Orchidopexy caused a decrease in ipsilateral testicular values and ameliorated the increase in hypoxanthine levels in contralateral testes. Conclusions: Replacing an intra-abdominal testis with its vas deferens ligated into the scrotum ameliorates the oxidative stress in both ipsilateral and contralateral testes. Since orchidectomy does not result in better contralateral testicular values, orchidopexy should be preferred when treating an undescended testis with vasal obstruction. Received: December 14,2001 Accepted after revision: June 18, 2002 Copyright (C) 2003 S. Karger AG, Basel.