A study was conducted of the respiratory health status of 475 rice farmers, 464 males, mean age 48.3 years (yr), in eight northern California counties. Subjects completed a questionnaire to provide information on demographic characteristics, specific rice farming activities and time spent performing these tasks, smoking, and respiratory symptoms that appeared to be related to their work. Indices of cumulative dust exposure were derived from the occupational information reported on the questionnaire. Pulmonary function testing was performed and chest X-rays were obtained. Most (94.8%) of the subjects were white. Approximately 9.5% were current smokers, 26.9% former smokers, and 63.6% were never smokers. The subjects had a mean of 25.7yr in rice farming. Chronic cough was reported by 7.1% of the subjects, chronic bronchitis by 6.3%, persistent wheeze by 8.8%, and hay fever by 25% of the subjects. Chronic cough was significantly associated with reported hours per year spent burning rice stubble. One second forced expiratory volumes (FEV1) and forced vital capacity (FVC) were both near the normal values. After adjusting for smoking status, however, FEV1s were significantly, inversely associated with reported years spent working with heated rice dryers. Midexpiratory flows (FEF25-75) were significantly decreased. After adjusting for age, height, and smoking status, rice storage activities involving work with unheated dryers was significantly associated with decrements in FEF25-75. Eighteen of 178 subjects (10.1%) had radiographic ILO opacity profusion scores of 1/0 or greater. After adjusting for age, however, no indices of exposure were associated with profusion scores of 1/0 or greater. The authors conclude that an increased prevalence of asthma exists among California rice farmers and the farmers have higher dust or fiber exposures than the general population.