This study of 130 subjects was performed to obtain more data about the smoking habits and levels of carboxyhemoglobin in various types of pipe and cigar smokers. These smokers may be divided by history into primary or secondary smokers and also into current inhalers and noninhalers. Prior studies of carboxyhemoglobin levels have yielded conflicting results, presumably due to differences in current habits of inhalation, which were often not taken into account. Cigarette, primary pipe, and secondary pipe inhalers had similar carboxyhemoglobin levels that were significantly higher than nonsmokers (5.6, 5.0, 5.4, and 1.0 percent, respectively). Cigar inhalers had markedly elevated concentrations of carboxyhemoglobin (13.8 and 11.8 percent in primary and secondary inhalers, respectively). Most secondary cigar and pipe smokers inhaled, whereas most primary smokers did not. Intentional inhalation, rather than past smoking history, is the most important factor in determining the carboxyhemoglobin level for each type of smoke.