Villagers residing in areas with rice farms are exposed to smoke from burning of agricultural waste that may affect respiratory health. To assess respiratory effects of this smoke-induced air pollution, a cross-sectional study has been conducted in three randomly selected villages of Isfahan rural areas. A physician-administered health questionnaire was completed for 433 male and 561 female villagers aged 1-80 years, followed by physical examinations and spirometry in symptomatic cases, before and after a rice burning episode in October 2000. Total particulate and respirable particulate maters (PM 10 was doubled during burning episode. Prevalence rates for respiratory symptoms before smoke were: recent asthma attacks (7.7%), using asthma medications (3%), sleep disturbed by dyspnea and cough (7.4%), exercise-induced cough (13.3%), which increased to 9.5, 7.1, 9.3 and 17%, respectively. Mean initial values (as percent of prediction) for; FEV1, FEV1/FVC, PEFR, and FEF25-75 were: 85.9 +/- 22.7, 81.7 +/- 8, 86.2 +/- 26.2 and 60 +/- 26.4, respectively. The mentioned values decreased to to 83.2 +/- 19.5, 76.5 +/- 10.3, 85.5 +/- 21.1 and 54.3 +/- 26.4, respectively. All of the clinical and spirometric changes were statistically significant. Study findings suggest increased respiratory morbidity associated with rice burning episodes among all people living in the area.