AIM: To study the protective effects of dexamethasone agains t ototoxicity of aminoglycoside antibiotics in guinea pigs. METHODS: Guinea pigs were divided into five groups. Group One: gentamycin, im; Group Two: amikacin, im; Group Three: gentamycin+ dexamethasone, im; Group Four: amika cin+ dexamethasone,im; Group Five: NS, im, all for two weeks. After three weeks, all animals were examined including tympanic mucous membrane reaction, nystagmu s depression rates and cochleae morphology. RESULTS: In Group Th ree and Four, the changes of morphology were slighter than those in Group One an d Two. CONCLUSION: Dexamethasone can weaken ototoxicity of amino glycoside antibiotics.