During the 1980s three comprehensive community-based heart disease prevention trials were conducted in the United States. The Stanford Five-City Project, Minnesota Heart Health Program, and Pawtucket Heart Health Program involved 12 cities; six received a 5-8 year multifactorial risk reduction program. This analysis pools data from the three studies to delineate the common intervention effects with greater sample size and power than could be attained by the single studies. Time trends were estimated for cigarette smoking, blood pressure, total cholesterol, body mass index, and coronary heart disease mortality risk in women and men aged 25-64 years. The joint estimates of intervention effect were in the expected direction in nine of 12 gender-specific comparisons; however, these were not statistically significant. The results illustrate the analytic challenges of evaluating community-based prevention trials and point to the smaller than expected net differences, rather than small sample size, as the reason for few statistically significant effects in the three U.S. prevention trials.