We conducted a descriptive study of a tobacco cessation program sponsored by a health maintenance organization (HMO) and led by primary care nurses. The tobacco cessation program was conducted at 20 primary care clinics in northeastern and central Pennsylvania. We gauged the successfulness of the program by the patients' self-reported quit rates at 1 year. We also examined the association between quit rates and compliance with scheduled counseling visits, the impact of the availability of an HMO pharmacy benefit that supported the costs of nicotine replacement therapy, and the quit rates among patients with HMO insurance versus those with insurance other than managed care. Of 1,695 patients enrolled in the program from July 1993 to March 1996, 1,140 completed 1 year of follow-up. Of these, 348 (30.5%) reported they had quit using tobacco. Among the 810 HMO enrollees who participated in the program, the quit rate was 280 (34.6%); among the 330 non-HMO participants, the quit rate was 69 (20.9%), a statistically significant difference (P < 0.001). For all patients, keeping more than four visits with the program nurse was associated with a significantly higher likelihood of quitting (317/751 [42.2%] versus 32/389 [8.2%]; P < 0.001). Non-HMO patients were less likely than HMO enrollees to keep four or more visits (165 [50%] versus 586 [72.3%]; P < 0.001). We were unable to detect a difference in quit rates among those with and those without a pharmacy benefit (196/577 [34%] versus 84/233 [36.1%]). These data are limited by their descriptive nature and the lack of information about other factors important in determining the quit rate among program participants. Nevertheless, they suggest that HMOs can successfully sponsor nurse-led tobacco cessation programs in multiple primary care settings and achieve 1-year quit rates significantly higher than the 15% quit rate reported in the medical literature. In addition, successfully quitting tobacco use appeared to be associated with use of counseling visits but not with use of a pharmacy benefit to pay for nicotine replacement therapy. Even though tobacco cessation programs have the best chance of benefitting HMO enrollees, patients not enrolled in managed care plans also appear to benefit significantly. This finding has important implications for developing future strategies--including the role of managed care organizations, the need to defray the costs of nicotine replacement therapy, and the best approach to provide counseling to patients--to meet the Healthy People 2000 goal of reducing tobacco smoking.