PIP: This article describes the systematic use of lay opinion leaders in the North Karelia project, a comprehensive community-based preventive cardiovascular program in Finland. Over 800 lay opinion leaders were trained to promote the reduction of heart disease risk factors and, after approximately 4 years, a survey was conducted to assess the long-term feasibility and self-reported effects. 267 of the 399 active lay workers surveyed were women; their median age was 52 years. The median age of the men was 50. 86% of the lay workers were married, and the majority lived in large villages. On the average they were members of 4 different associations or organizations and had acted as lay health workers for an average of 4 years. About 10% of these workers stated that they had had coronary heart disease themselves, and hypertension had been diagnosed in 19%. Only 2% were current smokers. The different types of milk they consumed was 1 indicator of their dietary habits: 14% too no milk at all, 23% skim milk/butter milk, 27% "low-fat" milk, 13% "consumption" milk (fatty milk), and 23% "full milk" (directly from the farm). 78% said they used butter on their bread. According to the lay workers' findings, 15% responded "very positively" and 60% "positively" in discussions about health matters; only 1% were reported as negative. There was little difference between the answers given by male and female lay workers. Discussions about physical activity were said to be the easiest, all other topics being only relatively easy. Although changes in health behavior were important, these workers saw clearly the difficulties in influencing people to accomplish these changes. Altogether 36% of the lay workers reported that at least 1 person had stopped smoking in association with their efforts, and 3% reported that as many as 6 or more persons had stopped smoking. This means that over 500 persons had over this period of time been influenced by the program to stop smoking. About 15-25% of the lay workers tried to promote action to restrict smoking in local bars, worksites, and at local meeting places. In bars this was rarely successful but in the other places some change often followed. The overall community impact of this volunteer lay worker activity cannot be assessed with certainty, but the overall evaluation of the project interventions in North Karelia from 1972-82 showed a major impact on behaviors and risk factors related to cardiovascular disease, i.e., a 28% reduction in smoking when adjusted for simultaneous changes in a matched reference area and a significant reduction in coronary mortality rates in contrast to the rest of the country.