The purpose of this study was to determine if hair nicotine and cotinine levels reflect relative exposure to environmental tobacco smoke (ETS) in subjects who worked in the hospitality industry, where public smoking was permitted. Hair samples from 26 subjects were analyzed by gas chromatograph/mass spectrometry techniques for nicotine and cotinine. An exposure gradient was shown for nicotine but not cotinine. Among nonsmokers, those working in bars where there are no public smoking restrictions had the highest hair nicotine levels, which were close to levels found in smokers. Nicotine measured in hair is useful as a biological marker for exposure to ETS from multiple sources. Bar workers in particular are exposed to high levels of ETS, which may adversely affect the health of nonsmokers.