This study was designed to evaluate the questionnaire-based prevalence and possible risk factors of occupational asthma among hairdressers in Turkey. We investigated occupational history and respiratory, ocular, dermal, and nasal symptoms using a standardized questionnaire, evaluated worksite pulmonary function tests, and performed allergen skin testing. We then determined asthma risk factors using age- and gender-adjusted logistic regression models. The prevalence of occupational asthma in hairdressers was 14.6%. The odds ratio for hairdressers in a high work intensity group was 3.6 (95% confidence interval, 1.2 to 10.9) with a significant dose-response trend (chi 2 trend = 4.875; P = 0.027). The odds ratio for occupational asthma among workers with atopy was 4.5 (95% confidence interval, 1.2 to 17.2). We also observed an excess risk of occupational asthma with allergic rhinitis and conjunctivitis. Occupational asthma did not differ among subgroups of hairdressers. We observed an important risk of occupational asthma among hairdressers. The most prominent risk factors were work intensity and atopy.