Background: cyclophosphamide is not only used as anticancer chemotherapeutic drug in adult and childhood malignancies, but also used as an immunosuppressive agent for organ transplantation. Aim of the work: this work was planned to evaluate the histological, immunohistochemical and ultrastractural changes in the testis of adult male Albino rats after administration of cyclophosamide and the possible role of vitamin E supplementation and drug withdrawal were explored. Materials and Methods: 50 healthy male Albino rats weighted 200gm were categorized into 5 groups, (ten rats each group). At the end of the experiment, the animals of all groups were anaesthetized by ether inhalation. Their testes were dissected out carefully and processed for light and electron microscope examination. The testes were immediately dissected out and the samples for light microscope were fixed in 10% neutral buffered formaldehyde (pH 7.2) for 24-72 hours. Sections (5um thick) were obtained and stained with H&E, Mallory's trichrome, PAS stains and immunohistochemicaly for detecting bcl-2 protein were used. Minute specimens were double fixed in glutaraldehyde and processed to obtain semithin sections stained with toluidine blue and ultrathin sections (70nm) for TEM. Results: testes of the cyclophosphamide-treated adult rats and cyclophosphamide withdrawal group revealed thick tunica albuginea, distorted and shrunken seminiferous tubules with wide interstitium in between. These tubules had marked reduction in the thickness of the germinal epithelium which appeared detached from irregular thick basement membrane and wide empty lumina were devoid of spermatozoa. The germinal epithelium in these tubules appeared degenerated with vacuolated cytoplasm and pyknotic nucle; the interstitium showed acidophilic hyaline material, congested thickened blood vessels and numerous interstitial Leydig cells with pyknotic nuclei. Cross sections of the middle and principle pieces of sperms showed disturbed axoneme. Cross sections in the sperms detected the middle, principle and end pieces. In the middle pieces, the axoneme was surrounded by fibrous and abnormal mitochondrial sheaths. The mitochondria in their sheath showed mild swelling, vacuolization and distortion. Leydig cells had large oval euchromatic nuclei with widened perinuclear space. The cytoplasm contained numerous mitochondria and dilated SER. using vitamin E with cyclophosphamide relatively improved the testicular tissue. Conclusions: cyclophosphamide treatment produced marked changes in the histological structure of the testes especially the germinal epithelium and sperms. This may lead to serious problems such as infertility or even sterility. The histological affection of cyclophosphamide on testis persisted after stoppage of treatment which is an indication of its cumulative effect. Supplementation of vitamin E with cyclophosphamide relatively improved the testicular tissue. So, administration of vitamin E in patient received cyclophosphamide is mandatory to reduce its side effects.