The lower morbidity and mortality of pipe smokers compared with cigarette smokers may be due to different inhaling patterns of pipe smokers. Plasma nicotine levels were determined in three groups of pipe smokers: (1) primary pipe smokers, (2) persons who smoke both pipes and cigarettes, and (3) secondary pipe smokers, ie, former cigarette smokers who now smoke pipes only. Primary pipe smokers inhaled minimally, as evidenced by low plasma nicotine concentrations after pipe smoking. In contrast, persons who smoke cigarettes and also pipes had high plasma nicotine levels after pipe smoking (mean, 22 ng/mL) and, hence, must have inhaled. Secondary pipe smokers (former cigarette smokers) had mostly low levels of plasma nicotine (mean, 6 ng/mL), suggesting that not all cigarette smokers continue to inhale when converting to pipe smoking. Pipe smoking may be safer than cigarette smoking in certain individuals.