Men with a background of unilateral torsion of testis (t.t.) show a greater percentage of infertility and changes in the spermiogram. Currently, the cause of contralateral testicle affectation remains unknown. With the aim of verify whether these changes are secondary to an immunological mechanism, the authors conducted experimental work in 3 groups of male rats, inducing a right t.t. over 24 hours, followed by detorsion and preservation of contorted testicle. Immunological response is determined through direct and indirect immunofluorescence reactions, including a brief description of the technique used. Positive reactions were obtained in both the spermatozoa's head and flagellum, more frequently in animals killed at 30 days and gradually decreasing in those killed at 60 and 90 days. The authors compare their results to other experimental works, and recommend to perform orchiectomy because of the damaging effect of the contorted testicle over the contralateral one.