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Objective: To determine whether measurement of cotinine in saliva is a sensitive measure of exposure to secondhand smoke (SHS) among customers in bars. Design: Before/after comparison of saliva cotinine and subjective assessments of SHS. Setting: Three bars in Wellington, New Zealand, June 2003. Participants: Eleven non-smoking medical students spent three hours in each location. They provided saliva samples before and after the visit, counted numbers of lit cigarettes in each bar, and assessed the smokiness of the venue. Samples were tested for cotinine using liquid chromatography coupled with mass spectrometry. Results: Cotinine levels post-visit were consistently higher than baseline. The mean difference was 1.03 ng/mL with a 95% confidence interval of 0.76–1.30 ng/mL. Adjustments to post-visit levels for metabolism and clearance of cotinine made very little difference to these results. Males tended to have higher baseline levels than females, and to show smaller increases. The bar with the greatest increase in cotinine was judged to be the smokiest on the basis of averaged cigarette counts and scores for presence of smoke and odour. Conclusion: The cotinine in saliva, when tested with the analytic methods described here, provides a means of assessing relatively short-term exposures to SHS.