The Stanford Five-City Project was initiated in 1978 to evaluate the effects of a community-wide health education program on cardiovascular risk factors, including blood pressure. Two treatment cities received an education program, which used the mass media, various community-based programs, and health professionals, designed to encourage individuals to learn their blood pressure levels, stay in the care of a physician if hypertensive, achieve ideal weight, exercise regularly, and reduce dietary sodium. Physicians were encouraged to follow national hypertension treatment guidelines and were provided with a range of patient education materials. To evaluate the effect of the intervention on cardiovascular risk factors, four independent cross-sectional surveys of randomly selected households and four repeated surveys of a cohort were conducted in both treatment cities and in two of the three control cities. After 5-1/3 years of intervention, blood pressure in the treatment cities exhibited an overall decline of 7.4 and 5.5 mmHg systolic and 5.0 and 3.7 mmHg diastolic in the cohort and independent surveys, respectively. These declines produced net changes between the treatment and control cities ranging from -1.1 to -3.8 mmHg. While the magnitude of these changes is not large, the results are significant from a public health perspective because they reflect changes in the overall community.