Surgical castration is done in male pet rabbits for reproduction control, to reduce inter-male aggression and to control hyper-sexuality, territory marking and aggression against humans. Alternatives to surgical castration are requested because of a relatively great anaesthetic risk in rabbits. Long-term application of a GnRH agonist implant results in a fully reversible "hormonal" castration in male dogs, cats, boars and many other species. Therefore, the present study using New Zealand White hybrid and German Giant rabbits aimed to investigate the effects of a 4.7mg deslorelin implant in peripubertal male rabbits (SG; n=10), as a mean of hormonal castration. Blood samples (for testosterone measurements), body weight and testicular volume were taken on days (D) 0, 14 and 90. Surgical castration was performed on D90 for testicular histology. Age-matched animals following the same protocol without implant administration served as adult controls (n=5, CG), animals castrated on D0 served as juvenile controls (n=7, JG). Following treatment, testosterone concentrations were not reduced compared to CG; basal testosterone concentrations were only measured in JG. Spermatogenesis was not affected in SG and not different from CG. Application of a slow release GnRH agonist implant does not induce hormonal castration in male rabbits over a period of 90 days indicating that it is not a suitable alternative to surgical castration in this species.