[en] A difference in the population of spermatogenic cells as well as in the diameter of the seminiferous tubules between the two regions, peripheral and central, in the normal testes of adult Swiss albino mice has been noticed. The independent response of the cell population and the tubular diameter, and their correlation of these tubules from both the regions have been studied after gamma irradiation (with 2, 3.5 and 5 Gy in 1, 3 and 5 days). The germ cell populations of both types of the tubules, peripheral and central, respond similarly and in parallel manner to these doses but tubular diameters behave entirely different from each other. The central tubular diameter tends to be affected soon after irradiation and started recovering while the peripheral ones showed a gradual shrinkage. Type B spermatogonia and resting spermatocytes were the types of cells amongst population found most vulnerable to the gamma rays. (author)