The protective effects of glutathione monoethylester (GEE) and GEE in combination with R-N6-phenylisopropyladenosine (R-PIA) were evaluated in the chinchilla when exposed to impulse (145 dB pSPL) or continuous (105 dB SPL, 4 kHz OB) noise. Six groups of 10 chinchillas were used as subjects. Before exposure to noise, the subjects were anesthetized, a 30 microl drop of drug was placed on the round window (GEE [50, 100, 150 mM], GEE 50 mM and R-PIA). Forty minutes later the subject was exposed to either impulse or continuous noise. The 50 mM treatment provided significant protection from impulse noise, but not from continuous noise exposure. The combination provided significant protection from both the continuous and impulse noise. In a separate set of experiments, glutathione (GSH) levels were measured in the perilymph. All the drug treatments elevated GSH levels. The results are discussed in terms of antioxidant treatments as a prophylactic measure against noise-induced hearing loss.