Int. J. Environ. Res. Public Health 2011, 8 260 Comparisons between the tobacco use prevalence of the ED patients and the general population are in Figure 2. The ED tobacco use prevalence was basically double the national and provincial averages up to age 44, almost 60% higher for 45–54 year olds nationally, and very similar to both the provincial and national averages for the oldest age groups (55+ nationally and 45+ provincially). Despite these elevated rates compared to national and provincial averages, the ED tobacco use rates were similar to age-stratified regional rates with a few exceptions—prevalence for ED patients 20–34 years in the NW Health Unit District was 12% (absolute) higher than the general population and prevalence for ED patients age 45–64 were 5–6% lower than the general population in both districts. 4. Conclusions This is the first study to systematically track the tobacco use prevalence in an entire ED population, present the prevalence stratified by age, and compare age-stratified rates to the general population using national, provincial, and regional comparisons. The findings revealed that despite an overall national downward trend in smoking nationally, from 50% in 1960 to 26% in 1999 [18] to 18% in 2008 [19], the rates in the participating communities remain high, at 1999 national rates. From a methodological perspective, the results show how important it is to consider age and rural-urban differences, and to make population comparisons that include data from the communities or regions being studied. Tobacco prevalence was high overall and across all but the oldest age groups, but “high” was relative to provincial and national comparisons because regionally, the rates were consistent with smoking rates in the general population. From an epidemiological perspective, it is not clear why the tobacco use rates for the oldest patients were the same as the national and provincial averages when the rates for younger patients were double that of national and provincial averages. There is no evidence that smokers in this region are quitting at a rate any faster than the national and provincial quit rates to explain the sudden drop to national averages for older patients; in fact, the prevalence rates in NW Ontario remain elevated, similar to the 1999 national rates [18], suggesting that people are not quitting as quickly. It is possible that smokers after age 55 are either moving away from these northern communities permanently or seasonally. Since tobacco is the primary preventable cause of premature death [20], it is also possible that some of the smokers are dying prematurely. Adding the tobacco use question to the ED registration as an electronic non-clinician-based system centralized the process of identifying and documenting tobacco use consistent with clinical practice guidelines [2], allowed standardization of the wording and location of tobacco use in the chart thereby contributing to the ease of data extraction and analysis, and resulted in the ability to systematically track the status of the entire ED population rather than only a select sample. The centralized approach also confined training to a small cadre of registration clerks and allowed a narrow focus on asking and documenting tobacco use rather than having to train a large number of clinicians who would have required a broader focus on asking about tobacco use and following through with the other components of the 5A brief intervention protocol (ask, advise, assess, assist, arrange) recommended by the Public Health Service (PHS) guideline [2]. The centralization also eliminated the need to rely on the workloads and willingness of a multitude of clinicians to ask and document tobacco use consistent with the PHS guideline. Although it was not done for this study, the centralized tobacco use question can be used to trigger cessation interventions by clinicians.