BACKGROUND: It is difficult and expensive to use surveys to obtain the repeatable information that is needed to understand and monitor tobacco prevalence rates and to evaluate cessation interventions among various subgroups of the population. Therefore, the electronic medical record database of a large medical group in Minnesota was used to demonstrate the potential value of that approach to accomplish those goals. METHODS: The relevant variables for all medical group patients aged 18 and over were extracted from the record from a 1-year period. Rates of smoking prevalence were computed for the entire population as well as for those with various characteristics and combinations of characteristics of interest to tobacco-cessation advocates. These prevalence rates were also adjusted to control for the other characteristics in the analysis. RESULTS: From March 2006 to February 2007, there were 183,982 unique patients with at least one office visit with a clinician, and a record of their tobacco-use status (90%). Overall, 19.7% with recorded status were tobacco users during this year, as were 24.2% of those aged 18-24 years, 16.0% of pregnant women, 34.3% of those on Medicaid, 40.0% of American Indians, 9.5% of Asians, and 8.5% of those whose preferred language was other than English. Combining characteristics allowed greater understanding of those differences. CONCLUSIONS: Although there are limitations in these data, the level of detail available for this large population and the ease of repeat analysis should greatly facilitate targeted interventions and evaluation of the impact.