Serum lipid levels are considered to be one of the main risk factors for cardiovascular diseases in middle-aged men and women. The significance, however, of serum lipid metabolism as a cardiovascular disease risk factor in the elderly has yet to be clarified. This paper focuses upon the serum lipid levels of groups of elderly people from 18 centres with diversified socioeconomic backgrounds in 11 European countries. Serum cholesterol was measured with an enzymatic colorimetric method by autoanalyser in one laboratory and accuracy was checked by participation in the quality control programme of the Centre for Disease Control, Atlanta, GA, USA. Mean (+/- SD) serum cholesterol levels ranged from 6.56 +/- 0.66 mmol/l (Bellinzona, Switzerland) to 5.22 +/- 0.68 mmol/l (Coimbra, Portugal) in men, and in women from 7.77 +/- 1.61 mmol/l (Elverum, Norway) to 5.86 +/- 1.07 mmol/l (Anogia-Archanes/Greece). The mean levels of high-density lipoprotein (HDL) cholesterol ranged from 1.40 +/- 0.58 mmol/l (Chateau Renault-Amboise, France) to 1.05 +/- 0.28 mmol/l (Elverum, Norway) in men and from 1.62 +/- 0.41 mmol/l (Padua, Italy) to 1.23 +/- 0.29 mmol/l (Anogia-Archanes, Greece; Vila Franca de Xira, Portugal) in women. The highest median serum triglyceride values were found in Norway (Elverum) (men: 1.50 mmol/l, women: 1.75 mmol/l), and one of the French groups (Chateau Renault-Amboise) had the lowest median values (men: 1.07 mmol/l, women: 1.15 mmol/l). Significant differences between participating centres and between sexes were found for the following variables: serum cholesterol, HDL, and the ratio total HDL cholesterol/total cholesterol. For triglycerides the differences were significant only between centres, not between the sexes.(ABSTRACT TRUNCATED AT 250 WORDS)