Objectives. To perform lung function tests on tobacco farm workers (TFWs) chronically exposed to flue curing and stacking of tobacco leaves and to compare them with vegetable farm workers (VFWs) who were not exposed to any known air pollutant (control). Design. Comparative study. Setting. Tobacco and vegetable farms. Subjects. 20 TFWs and 30 VFWs. All subjects were male and the mean age, height and weight of the two groups were not significantly different. Outcome measures. Lung function indices. Results. Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV 1 ) and peak expiratory flow rate (PEFR) of the TFWs were 3.28 +/- 0.51 litres, 2.68 +/- 0.74 litres and 6.41 +/- 2.08 litres/second, respectively. These figures were significantly lower than 3.97 +/- 0.83 litres, 3.09 +/- 0.71 litres and 8.62 +/- 2.74 litres/second, respectively, for the control subjects (P < 0.01, 0.05 and 0.01, respectively). However, mean FEV 1 as a percentage of the FVC (FEV 1 %) of the TFWs was not significantly different from that of the controls. FVC of the TFWs declined with duration of service (r = 0.74; P < 0.01). Conclusion. The results are indicative of restrictive lung defect in the TFWs and may be attributed to long-term exposure to flue curing and stacking of tobacco leaves. The results also suggest the importance of the duration of exposure in the aetiology of lung impairment in this environment.