This study was designed to measure auditory function in patients with chronic obstructive pulmonary diseases (COPDs) who generally suffer from chronic hypoxemia. Control and COPD subject groups received a battery of tests to assess overall hearing sensitivity and peripheral (end-organ and eighth-nerve) and brain-stem auditory function, as well as blood-gas analysis. Results showed a statistically significant difference for all audiological measures between the control group and a COPD subgroup--the presumptive hypoxic subjects (partial oxygen tensions, PO2, <75 mm Hg). Correlation analyses of results from all subjects (regardless of PO2) also revealed significant covariance with PO2 for overall, RMS, amplitude of click-evoked otoacoustic emissions (RA), hearing threshold level, and auditory brain-stem response (ABR, I-V inter-peak latency). Chi2 or Fisher's exact tests were statistically significant for frequencies of cases classified according to a criterion PO2 of 70 mm Hg (putative critical O2 for completely normal auditory function) and either hearing thresholds falling below or RA values above 1.5 standard deviations of the control-group means, respectively. However, chi2 was not significant for a comparable criterion of ABR I-V IPL. In general, clinically significant hearing loss was uncommon in COPD patients, and the observed effects represented relatively small changes in the auditory measures examined. Still, overall, changes were in the direction of poorer function, and these results suggest physiologically significant impact of chronic hypoxemia and the need for further study to evaluate thoroughly this medical condition as a potential risk factor for audio-vestibular dysfunction.