The seasonal testicular changes in the Soft‐shelled turtle,T. sinensis,show a well‐marked temporal differentiation between the functional activity of the seminiferous tubules and the interstitial tissue. In the March‐April breeding period, the interstitial cells are large and lipid‐free, with rounded turgid nuclei and a strongly positive reaction to tests for A5‐3P‐hydroxysteroid dehydrogenase. As might be expected with such histochemical manifestations of high androgen secretory activity, the epididymis is also highly developed during this period. In contrast, the seminiferous tubules are regressed, spermatogenetically inactive, and heavily lipoidal. Fertilization is achieved by spermatozoa discharged from the epididymidal canals.Immediately following the breeding period, the interstitial tissue atrophies and becomes strongly lipoidal and negative to tests for 3P‐HSD. This interstitial regression is accompanied by the regression of the epididymides and a concomitant recrudescence of seminiferous tubule activity. The latter rapidly become depleted of their lipid and become strongly positive to tests for 3P‐HSD. Spermatogenesis resumes, and the seminiferous tubules become filled with representatives of all the germinal stages by the end of May. In early autumn there is a cessation of spermatogenesis, and, as the epididymides recover under the influence of a recovering androgen secretion by the redeveloping interstitial cells, the spermatozoa become evacuated from the tubule‐lumina to the epididymidal canals, where they remain until the succeeding breeding season.The seasonal histochemical events are discussed in relation to the basic pituitary‐gonadal regulation of