The objectives of this study were: 1) to determine if chlorine exposure at low levels induces nasal effects in humans as it does in rodents; and 2) to establish a possible occurrence of respiratory effects in human volunteers exposed to chlorine vapour at concentrations of 0, 0.1, 0.3 and 0.5 ppm. The study was conducted in a double-blind fashion in 8 male volunteers using a repeated measures design, with randomly selected exposure sequences. Subjects were exposed for 6 h x day(-1) on 3 consecutive days to each of the 4 exposure conditions. In nasal lavage, interleukin-8 (IL-8), albumin, total cell number, and percentages of neutrophils, lymphocytes, monocytes, eosinophils, and epithelial cells were determined. The lung function parameters that were analysed included forced vital capacity (FVC), forced expiratory volume in first second (FEV1), FEV1/FVC ratio, and maximal mid expiratory flow (MMEF). Data analysis was limited to 7 subjects since one volunteer decided to stop participating for reasons not related to the study. Nasal lavage measurements did not support an inflammatory response or irritant effects on the nasal epithelium. For FVC, FEV1, and FEV1/FVC, no significant differences were found. MMEF was significantly different between the 0 and 0.5 ppm exposure, but this was attributed to an unexplained shift in baseline values during control (0 ppm) exposure. The present data does not support an inflammatory effect in the nose nor shows changes in respiratory function at repeated exposure up to 0.5 ppm. This discrepancy with previous data in rodents can be attributed at least in part to differences in respiratory tract airflow characteristics.