Abstract : Cyclophosphamide(CTX) is an alkylating chemotherapeutic drug with immunosuppressive activities. It is a toxic drug which targets both the cancer cells and also the normal cells. The objective is to study the dose at which harmful effects of CTX are caused on testes, liver and kidney tissues. A total of 55 male Wistar rats were divided into eleven groups comprising 5 animals each. Animals in group 1 (control group) were given 1.5mls Phosphate Buffered Saline (PBS) solution weekly for 4weeks. Animals in groups 2-11 were given CTX at 25.1, 50.2, 75.3, 100.4, 125.5, 150.6, 175.7, 200.8, 225.9, 250.0mg/kg body weight orally weekly for 4weeks. They were then sacrificed 4hours after administration on the fourth week. The testes, liver and kidney tissue were processed, sectioned and stained with H&E. Significant pathological changes were seen after 4weeks. The changes were more prominent as the dosage of CTX administered increased. These pathologies ranged from mild to severe atrophy of spermatogonic epithelium with or without preponderance of round spermatids in the lumen, moderate to random periportal fibrosis with centrilobular cord atrophy and pyknosis of hepatocytes, atrophy of tubular epithelial cells with severe interstitial inflammation and tubular epithelial necrosis. The pathological changes were observed in the histology of testes, liver and kidney following increase in the dosage of treatment among groups. Hence, a regular semen analysis and testicular hormonal assay, regular liver and kidney function test are encouraged in patients taking chemotherapeutic agents like CTX with possible concurrent administration of repro-protective, hepatoprotective, and nephroprotective agents.