en Physiology Physiology Original Research Original Research The discovery of the antifertility activity of gossypol led scientists and researchers to the development of compounds with antifertility activity that can be used as male contraceptives. These studies resulted in discovery of the antifertility activity of several classes of compounds which have been reported in the literature. This article deals with the synthesis of four new analogues of pyrimethamine, the derivatives of 2, 4-diamino-5 (3,4-dichlorophenyl)-6-alkyloxymethyl pyrimidine (methyl ethyl, n-propyl, iso-propyl), and the results of experimental antifertility evaluation of these compounds on male rats, which revealed a significant decrease in motility, viability, ESR and DSP indices in treated animals 2, 4-Diaminopyrimidines; Male contraception; Male reproduction; Spermatogenesis; Fertility 27 32 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-298-419&slc_lang=en&sid=1 H SADEGHIPOUR ROODSARIE 20031947532846005823 20031947532846005823 Yes From the Departments of Physiology Tehran University of Medical Sciences. Tehran. I.R. lran. M VOSOOGHl 20031947532846005824 20031947532846005824 No From the Departments of 'Medicinal Chemistry Tehran University of Medical Sciences. Tehran. I.R. lran. M ZAHRAIE 20031947532846005825 20031947532846005825 No From the Departments of Clinical Biochemistry. Tehran University of Medical Sciences. Tehran. I.R. lran.