OBJECTIVES: This study was conducted to investigate that the chronic noise exposure is associated with decreased serum magnesium concentrations and evaluate whether decreased serum magnesium is associated with noise induced hearing loss. METHODS: One hundred seventy-eight male workers exposed to noise were selected and classified three groups by the degree of hearing loss. Hearing threshold levels were less than 30 dB at 1,000 Hz or less than 40 dB at 4,000 Hz in group I, more than 30 dB at 1,000 Hz or more than 40 dB at 4,000 Hz and 15 dB and less of pure tone average(PTA: (500 Hz+1,000 Hz+2,000 Hz)/3) in group II, more than 30 dB at 1,000 Hz or more than 40 dB at 4, 000 Hz and over 15 dB of PTA in group III. RESULTS: Serum magnesium concentrations were 2. 42+/-0. 26 nc/dt in group I, 2. 35+/-0.23 mg(dl in group II, 2.26+/-0.24 ne/dl in group III, respectively and significantly different between group I and group III (p<0. 01). It was negatively correlated with duration of the noise exposure as correlation coefficient(r) of -0.194 (p<0.05). Analysis of the multiple regression on hearing threshold levels showed that serum magnesium, diastolic blood pressure, duration of the noise exposure were statistically significant at 4,000 Hz(p<0.05). While only age was statistically significant at 1,000 Hz(p<0.05). CONCLUSIONS: These results suggest that chronic noise exposure may induces decrease in serum magnesium concentrations and that its decreased concentration is related with noise induced hearing loss.