The numbers of deaths attributed by tobacco smoking have remarkably increased, reflecting the smoking patterns of previous decades. Exposure to environmental tobacco smoke increases the prevalence of both upper and lower respiratory tract illnesses. Self-reports of direct and indirect smoking may not always be reliable in questionnaire method used epidemiology. A number of biochemical makers have been used to validate claims of indirect smoking among which the most widely used specific markers has been the nicotine metabolite cotinine. This study was conducted to evaluate the cotinine levels to determine smoking status. Biomoitoring to assess the validity of questionnaire method found that sensitivity and specificity coefficients of around 100% and 100% in direct smokers. On the other hand, sensitivity and specificity coefficients were 56.74% and 47.26%, respectively. This results suggest that indirect smoking status should be assessed by biomonitoring such as cotinine levels. Keywords : smoking, exposure, nicotine, cotinine