Flour dust is a heterogeneous substance with respiratory sensitizing properties; its long-term exposure may cause acute or chronic respiratory diseases. Therefore, the aim was to investigate the dose response effects of flour dust on lung function. An additional objective was to minimize the potential health risks in flour mill workers by providing them with information about the hazards of flour dust. Pulmonary function was studied in forty-six male flour mill workers who worked without the benefit of flour dust control ventilation or respiratory protective devices and a similar number of male control subjects. All participants were non-smokers and were matched for age, height, weight and socio-economic status. Pulmonary function tests were performed by using an electronic Spirometer and results were compared by a paired t-test. The present study results showed a significant decrease in the mean values of FVC, FEV(1), PEF and MVV and this impairment was increased with duration of exposure in the flour mills. This group of flour mill workers had occupationally related pulmonary function impairment and stratification of results showed a dose response of years of exposure in flour mills on lung function.