In summary, I think the National Cholesterol Education Program could be strengthened if more realistic values for normal and abnormal serum cholesterol levels were adopted, if lipoprotein typing were recommended as an early step in the screening process, if modification of other risk factors were attempted, and if intervention with diet were avoided for persons without other risk factors whose cholesterol levels are below 6.21 mmol/L. A more flexible program of diet therapy should be offered to those persons with serum cholesterol values over 6.21 mmol/L, which should include not only the "prudent diet" but also other dietary regimens with proven benefits. All physicians should make an attempt to carry out this program of preventive cardiology as a long-term clinical investigation to determine the extent to which modification of serum lipid levels in large outpatient populations influences the prognosis for CHD.