Acute changes in ventilatory function during a workshift with exposure to hemp, flax, and cotton dust were measured on Mondays in a group of 61 textile workers, all working on carding machines. In addition, single-breath diffusing capacity (DLCOSB) was measured before dust exposure on Monday in 30 of the 61 workers. Large acute reductions during dust exposure were recorded in maximum expiratory flow rate at 50% VC (MEF50%), ranging from 38 to 22%. Acute reductions of FEV1-0 were considerably smaller, ranging from 17 to 9%. There was a statistically significant increase in residual volume (RV) with very small and insignificant changes in total lung capacity (TLC). Although preshift FEV1-0 and FVC were decreased, DLCOSB was within normal limits. Plethysmographic measurements in six healthy volunteers exposed to hemp-dust extract confirmed the results obtained in textile workers, that is, that TLC does not change significantly during dust-induced airway constriction and that maximum expiratory flow rate at 50% VC (MEF50%) is a more sensitive test than FEV1-0 in detecting acute ventilatory changes caused by the dust extract.