This study was carried out the exploitation of allergic history and clinical examination with dermal test of 780 textile workers to determine the cause of cotton dust induced asthma. Which was showed that 6.28 percent of worker suffered cotton dust induced asthma, primarily in department with high degree of cotton dust pollution. Major clinical symptoms and signs were chest's tightness (100 percent) , wheezing (100 percent), pulmonary stridor by auscultation (79.59 percent), cough with sputum (40.81 percent) which occurred frequerztly at working time and reduced or disappeared completely after working time. Of asthmatic workers, prick-tests with cotton allergen were positive in 67.35 percent of cases and intradermal tests were positive in 93.88 percent. The authors recommended to perform the prick-test first and only perform intradermal test when prick test ins negative or suspected.