Ultrastructural study of ototoxicity is well documented with two points of interest : organ of Corti for aminoglycosides and stria vascularis for loop diuretics. The severe ototoxic interaction of the combined administration of furosemide and kanamycin was studied in rats. Severe damage occurred in the inner ear when both furosemide and kanamycin were administered to rats. Sprague-Dawley strain rats each weighing 200-220gm and hearing normal Preyer reflex devided into three groups. All groups of animals were administered same dose of kanamycin (300 mg/Kg intramuscularly) and furosemide (30 mg/Kg intraperitoneally). Group I was administered kanamycin and furosemide at same time. Group II was administered furosemide 1 hour later after kanamycin injection. Group III was administered furosemide 3 hours later after kanamycin injection. A very high level of degeneration was found in the organs of Corti of rats who were administered of furosemide 1 hour later (Group II) to rats pretreated with kanamycin. A degeneration appeared first on the outer hair cells in the basal turn of the cochlear starting with an increase in lysosomes, degeneration of mitochondria in the subcuticular area and resulted in atrophied outer hair cell, loss of hair cell and degenerated outer hair cell with numerous vacuoles and ruptured nucleus. Marginal cells of the stria vascularis had various vacuole and were protruded into the endolymphatic space. Atrophied intermediate cel with invagination of nucleus was present.