The prevalence of respiratory symptoms and changes in ventilatory capacity were studied in 84 female (mills A and B) and 27 male hemp workers employed in textile mills. Forty-nine women and 30 men from a non-dusty industry served as controls. A significantly higher prevalence of almost all chronic respiratory symptoms was found in exposed female workers compared to controls. For men the differences were significant for nasal catarrh and sinusitis. A high prevalence of byssinosis was found among female workers in both mills (A = 47.8%); B = 57.9%) as well as in male workers (66.7%). Statistically significant acute across work shift reductions in ventilatory capacity were found for all measurements in female and male hemp workers (P greater than 0.01) varying from 7.1% for FEV1 to 15.1% for FEF50. Measured Monday baseline values before the work shift were significantly lower than expected for hemp workers being particularly reduced for FEF25 and FEF50. The data suggest that exposure to hemp dust is a major risk factor for the development of occupational lung disease.