The relationship of the risk of cancer and death to total serum cholesterol was studied in a random population sample from two counties of Eastern Finland. Data on total serum cholesterol were recorded between February and April 1972 for 3745 men and 4221 women aged 30 to 59 years who had no history of cancer, diabetes, or cardiovascular or cerebrovascular disease in the preceding 12 months. The participating rate in the survey was 92% in men and 94% in women. During six years from January 1, 1973 to December 31, 1978, cancer occurred in 65 men and 78 women at risk and 130 men and 52 women died of any disease. The risk of cancer bore no relationship to serum cholesterol either in men or in women. In men, the risk of death due to any disease and coronary heart disease rose steadily with increasing serum cholesterol from the level of 270 mg/dl (7.0 mmol/liter), whereas in women there was no association between serum cholesterol and the risk of death.