Measurements of total dust concentration were made in a western red cedar sawmill that employed 701 workers. Both area sampling and personal sampling of total dust were done over an 8-hr shift corresponding to job descriptions and locations to assign each worker an exposure level. A total of 652 (93%) of the workers completed a respiratory-occupational questionnaire and performed spirometry, of whom 334 were assigned an exposure level. Dust exposure ranged from undetectable to 6.0 mg/m3 with a median exposure level of 0.2 mg/m3. Only 10% of the workers with an assigned exposure level were exposed to more than 1.0 mg/m3. Work-related asthma, defined as symptoms of asthma which improved on days off work, was reported by 52 workers (8.0%) and was more prevalent after 10 or more yr of employment. Chronic cough, dyspnea, persistent wheeze, and physician-diagnosed asthma were unrelated to either work duration or exposure. Levels of forced vital capacity (FVC) and forced expiratory volume in 1 sec (FEV1.0) were lower with dust concentrations greater than 2.0 mg/m3, controlling for age and smoking; maximum mid-expiratory flow rate (FEF25-75%) and FEV1.0/FVC were unrelated to dust exposure concentration. Work-related symptoms of eye irritation were seen more commonly with exposure to dust concentrations of 3.0 mg/m3 or more. It is concluded that symptoms of work-related asthma in red cedar workers are more common after 10 yr of exposure, and that levels of pulmonary function are lower with higher wood dust exposures.