Tailored communications are one of the most promising approaches to smoking cessation interventions for entire populations. Assessments based on the Transtheoretical Model are processed by computer-based expert systems that generate feedback reports tailored to each individual to accelerate their progress through the stages of change for smoking cessation. Seven studies are reviewed that range from a more traditional clinical trial to trials on entire populations of smokers to population trials designed to change multiple behaviours, including smoking. A series of three tailored communications was found to produce long-term point prevalence abstinence rates within the narrow range of 22-26% abstinence. This same range of abstinence was found even when two or three other behaviours (e.g. diet and sun protection) were treated in the population. These results point to a future in which health behaviour risk interventions will be assessed not solely by their efficacy but by their population impact.