Background: Several studies have been conducted to estimate the population prevalence of hypertension, or its diagnosis and treatment. There is no multinationally comparable information on the prevalence of hypercholesterolaemia, or its diagnosis and treatment, since individual studies are often not directly comparable. Methods: Data from the WHO MONICA Project's final risk factor surveys were used. Data were collected using standardized methods between 1989 and 1997 for the 35-64 year age range in 32 populations, in 19 countries on 3 continents. Results: The prevalence of hypercholesterolaemia (total cholesterol ?6.5 mmol/l or taking lipid-lowering drugs) varied across populations from 3% to 53% in men, and from 4% to 40% in women. Awareness of hypercholesterolaemia varied from 1% to 33% in men, and from 0% to 31% in women. In most populations, over 50% of men and women on lipid-lowering drugs had a cholesterol level