The bleachery procedure is the most frequent method used to decolorize denims since sandblasting has been shown to cause silicosis. The aim of this study was to determined the prevalence of occupational asthma among denim bleachery workers in Kayseri. The study was conducted in 4 factories, in which jean bleachery was performed, in Kayseri between December 2008 and February 2009. Overall, forty-four subjects, 22 from the bleachery section and 22 from the other sections, were included. A questionnaire about respiratory symptoms was administered. Pulmonary function tests (PFTs) and serial peak expiratory flow (PEF) measurements were performed. All subjects were evaluated by posteroanterior chest x-rays. The prevalence of occupational asthma (OA) in the bleachery and other section workers was 23.8% and 9.1%, respectively (p> 0.05). Within workers, exercise dyspnea (23.3%) and wheezing (20.9%) were the most frequent symptoms. The relationship between the duration of employment and PFTs in bleachery workers (n= 21) was negatively correlated and statistically significant with FEV1, FEF25-75 (moderate; r= -0.477, -0.449, respectively; p< 0.05) and FEV1/FVC, FEV1% (well; r= -0.588, -0.509, respectively; p< 0.05). The results of the present study suggest that exposure to denim-bleaching agents plays an important role in the occurrence of respiratory symptoms, reduction in pulmonary functions, and induction of occupational asthma.