Cyclophosphamide (CP), is cytotoxic alkylating agent, used extensively as an antineoplastic agent for the treatment of specific types of cancers, as well as an immunosuppressive agent during organ transplantation . However, its clinical utility is limited because of its several adverse actions especially on the human reproductive system. Cyclophosphamide treatment in patients is associated with oligozoospermia and azoospermia, as well as biochemical and histologic alterations in the testes and epididymis of rats and humans. Melatonin hormone is natural compound found in humans and animals ,it was detected in the reproductive system of human and animals ,therefore it seems reasonable to assume that melatonin may play a useful function to the cells of the reproductive system . Aim of this work was to investigate the effect of melatonin on the histological and immunohistochemical changes which may appear in the testicular cells of the testes of albino rats previously treated with cyclophosphamide alone or in combination with melatonin . Material& Methods :forty two adult male albino rats weighing about 150 -200 gm were enrolled in this study .The animals were classified into three groups .At the end of experiment ,the rats were sacrificed ,weighted ,right testes were processed for paraffin section. Prepared histological slides were stained with H & E, Masson’s trichrome ,Immune histochemical studies with BCL2 onchoprotein and Morphometric study .Results showed certain histological and immunohistochemical changes concerning that melatonin could exhibit partial protection against cyclophosphamide induced testicular atrophy.