The aim of the study was to identify specific health risks and exposure-response relationships associated with exposure to metalworking fluid (MWF) aerosols. In a cross-sectional study of machine workers exposed to MWF aerosols in five companies in Sweden, a self-administered questionnaire about health symptoms, work tasks, and exposure situations was sent out to 2294 employees, 1632 exposed and 662 referents. Referents were office workers and metal workers not working with MWFs. In four of the companies, there were recent measurements of personal exposure to MWF aerosols. Log-binomial regression models were used to estimate prevalence ratios with 95% confidence intervals for different health outcomes in relation to different variables of exposure. The response rate after two reminders was 67% resulting in 1048 (923 male, 125 female) workers exposed to MWF aerosols and 451 (374 male, 77 female) referents. The study indicates that metal workers in Sweden currently exposed to a mean value of MWF aerosols of 0.4 mg m(-3) have a significantly higher prevalence of wheeze, chronic bronchitis, chronic rhinitis, and eye irritation compared to the referents. At a mean exposure of 0.4 mg m(-3), a level below the Swedish 8-h exposure limit value of 1 mg m(-3), machine operators showed increased prevalence of symptoms in eyes and airways. Thus, the current exposure limit value does not seem to protect the workers from such symptoms.