--To evaluate the effectiveness of a model blood cholesterol screening program. --Principal components included physician education, community-based screenings, and follow-up. A lay or professional educator provided counseling and referral advice. Half of the subjects with high blood cholesterol levels received a reminder to see their physician. --135 sites in four Massachusetts communities. --10,428 adults. Males, the young, the poor, the less educated, and minorities were underrepresented. --Referral completion rates, blood cholesterol changes. --51.5% of those referred had visited their physicians within 2 to 4 months, increasing to 65.6% within 6 to 12 months. Older age (odds ratio [OR], 1.17 per additional decade), more education (OR, 1.17 per additional level), higher blood cholesterol levels (OR, 1.19 per additional 0.51 mmol/L), previous knowledge of level (OR, 1.34), and receiving a reminder (OR, 1.24) were significantly associated with greater likelihood of referral completion, whereas the type of educator providing counseling was not. Physicians had remeasured the blood cholesterol level of 76% of those seen, given dietary counseling to 70%, and prescribed medication to 15%. Significant changes in dietary fat were reported by both compliers and noncompliers with advice to follow up with their physicians. Six months after screening, blood cholesterol levels were 3.6% lower in noncompliers, 4.4% lower in compliers not taking cholesterol-lowering medications, and 8.8% in compliers taking such medications. --An effective, community-based blood cholesterol screening program can attract diverse populations and can result in most participants with high levels following up with their physicians, making dietary changes, and lowering their cholesterol levels. Additional strategies may be needed to attract underrepresented groups and to reduce the apparent overuse of cholesterol-lowering medications.