In 1972 the Stanford Heart Disease Prevention Program launched a three-community field study. A multimedia campaign was conducted for two years in two California communities (Watsonville and Gilroy), in one of which (Watsonville) it was supplemented by an intensive-instruction program with high-risk subjects. A third community (Tracy) was used as a control. The campaigns were designed to increase participants' knowledge of the risk factors for cardiovascular disease, to change such risk-producing behavior as cigarette smoking, and to decrease the participants' dietary intake of calories, salt, sugar, saturated fat, and cholesterol. Results of a sample survey indicate that substantial gains in knowledge, in behavioral modification, and in the estimated risk of cardiovascular disease can be produced by both methods of intervention. The intensive-instruction program, when combined with the mass-medica campaign, emerged as the most effective for those participants who were initially evaluated to be at high risk. The results after two years of intervention are reported for effects on knowledge and behavioral change for the total participant samples and for the high-risk subsamples in each of the three communities.