Abstract: "Objectives: this study is designed to assess the effect of occupational exposure on respiratory symptoms and pulmonary functions of workers in Sudanese factories. Methods: A cross sectional study was performed in four Sudanese factories, in Khartoum and Eight hundred and six workers from different factories were included,319 workers from Khartoum refinery company, Khartoum state, 232 workers from Al Genaid sugar factory, 152 workers from Al Baraka biscuit manufacturing factory and 103 workers from Gezira tannery, Gezira state . Respiratory symptoms, pulmonary function and skin prick tests were evaluated.