In clinical practice cystitis resulting from systemic administration of cyclophosphamide may be life threatening or fatal. In a retrospective study of 444 patients with gynmcological tumours treated with cyclophosphamide, 101 patients developed overt cystitis and 10 of these patients died from causes directly attributable to the cystitis (Spechter 1965). The histological changes of cyclophosphamide cystitis consist of edema of the bladder wall, infiltration with polymorphonuclear leukocytes and submucosal hiemorrhages from dilated thin walled vessels (Fontana-Donatelli 1963). An Experimental Model of Cyclophosphamide Cystitis All of the experiments were conducted with adult female Wistar rats of the Royal Postgraduate