Introduction: The aim of this study was to evaluate contralateral testicular damage (CTD) following unilateral blunt testicular trauma (BTT) and testicular capsule laceration (TCL) by the serum inhibin B level which is an accepted marker of spermatogenesis. Methods: Fifty peripubertal male Wistar albino rats were divided into 5 groups each containing 10 rats. Group 1 was the control group. Group 2 was the BTT group in which the right testicle was placed on a firm surface and a metal rod weighing 215 g was dropped onto the testicle from a height of 5.5 cm. Group 3 was the TCL group in which right testicular tunica albuginea was lacerated using the needle of 4/0 silk suture. Group 4 had right orchiectomy initially. Group 5 was the sham group. In all groups, 3-ml blood samples were taken and bilateral orchiectomies were performed 6 weeks after initial manipulations. Results: Groups 2 and 3 had decreased inhibin B levels (p < 0.001), although the orchiectomy group had normal levels. Histological analyses showed lower Johnsen scores for both trauma groups in the ipsilateral and contralateral testes (p < 0.05). Conclusions: Serum inhibin B levels decrease following unilateral testicular trauma reflecting CTD. Copyright (C) 2003 S. Karger AG, Basel.