As part of a randomized trial that compared the effects of three physician-delivered smoking interventions on patients' long-term cessation rates, we examined factors associated with the extent of baseline cigarette smoking separately in 546 men and 715 women who were enrolled in this trial. Several baseline characteristics were significantly related to heavier (> or = 25 cigarettes per day) smoking after controlling for a variety of factors in multivariate analyses, which were performed separately for men and women. Among both men and women, extent of addictiveness to smoking and number of cigarettes smoked during periods of heaviest smoking were significantly related to extent of current cigarette smoking (p < 0.001). In addition, among men shortness of breath, lack of previous attempts to quit and lack of confidence in their ability to stop smoking were significantly related to current heavy cigarette smoking (p < 0.05). The results of this study in ambulatory outpatients suggest a profile of heavy cigarette smokers that may be used for the more effective delivery of targeted smoking intervention efforts.