Journal Article ; Research Support, N.I.H., Extramural ; Smokeless tobacco use in the form of the betel quid is common in the Western Pacific Region, and yet few studies have determined the nicotine delivery of this habit. During a validation substudy, we randomly sampled 201 adults from a rural province of Cambodia and determined nonparametric (bootstrapped) confidence intervals (CIs) for salivary cotinine levels in tobacco users. We found that cotinine levels for daily betel quid use among women (95% CI = 218.6-350.0 ng/mL) were (1) similar to the levels for daily cigarette smoking in men (95% CI = 240.2-317.1 ng/mL) and (2) significantly higher than the levels for daily cigarette smoking in women (95% CI = 71.8-202.7 ng/mL). The 95% confidence range for these habits exceeded the threshold for addiction. Our findings from rural Cambodia indicate that the typical betel quid habit among women supports the same level of nicotine addiction as the typical cigarette habit in men.