Nitrogen-dioxide (10102440) (NO2) was measured using passive samplers and respirable particulate was determined gravimetrically over the shift for 232 workers in four diesel bus garages on the same day as pulmonary function tests and questionnaires were administered, in order to relate changes in pulmonary function and work related symptoms that occur over a shift and the association of these changes with exposure to diesel exhaust. The prevalence of acute symptoms ranged from 15 to 54 percent, being elevated above expected only in the high exposure group and in two garages. Prevalence and exposure were most strongly associated with the symptoms of eye irritation, labored breathing, chest tightness, and wheeze. Except for wheeze, the younger the age the higher the prevalence of symptoms. Smoking was associated only with cough and wheeze, being elevated above expected among only the current smokers. When compared to workers in a lead acid battery plant, the prevalence of eye symptoms, headaches, difficult or labored breathing, nausea, and wheeze were higher among the garage workers, while the prevalence of sneezing was higher among the battery workers. No significant changes in pulmonary function were detected. Eye irritation was the most sensitive of the symptoms investigated. NO2 exposure was below 1.5 parts per million, which was apparently below the threshold for producing a measurable reduction in lung function.