Abstract: The testicular histology of the lizard, Uromastyx aegyptius microlepis were varied considerably during hibernation and activity periods, reaching maximum values in summer. The onset of winter induces testicular regression, reduced testis size, testis diameter, diameter and epithelial height of the seminiferous tubules and epididymal epithelial height. Animals exhibit testicular recrudescence during late winter (February and March) and maximum testicular volume occurred during June. The period of maximal testicular volume was positively correlated with increasing ambient temperature. The summer season induces the testicular activity in contrast with the winter season in which the activity decreased and the testes were collapsed. Spermatocytogenesis is active in early spring and the major portion of the seminiferous epithelium comprises spermatids in various stages of maturation and their luminae were filled with spermatozoa. The size of the interstitial cells is direct correlated with changes occurring in epididymis and seminiferous epithelium. Most interstitial cell nuclei show clear regression when spermatocytogenesis were diminishes.