The second population survey of the Swiss MONICA project took place in 1988-89 in the cantons of Vaud, Fribourg and Ticino. Blood lipids (total, LDL, and HDL cholesterol as well as apolipoproteins A-I and B) were measured in 3341 individuals aged 25-74 years belonging to a representative sample of the three cantons' population. Total and LDL cholesterol values were high on average, especially among patients aged 45 and over: total cholesterol was > 6.5 mmol/l in 27% (age 25-34) to 58% (age 45-54) and in 15% (age 25-34) to 64% (age 65-74) of men and women, respectively. HDL cholesterol values were relatively stable with age, at a higher level in women (median 1.5 mmol/l) than in men (median 1.2 mmol/l). To summarize, about 1 out of 5 people had cholesterol values placing them at low risk for the development of coronary heart disease, whereas 1 out of 4 were at increased risk. Apolipoprotein B, a component of LDL cholesterol, and apolipoprotein A-I, a component of HDL cholesterol, were measured for the first time in a large representative sample of the Swiss population. The distribution of both apolipoproteins was, in the aggregate, very similar to the distribution of the corresponding LDL and HDL cholesterol. A comparison of cholesterol values measured in 1988-89 with values previously measured in the same population (MONICA population survey 1984-85) did not show any reduction with time.