To determine lipoprotein (LP) abnormalities, clinical characteristics and preclinical signs of atherosclerosis in asymptomatic subjects with hyperlipidaemia serum cholesterol and triglyceride (TG) concentrations were determined in 20,000 subjects attending a health control centre linked to their employment. 2. Three hundred and fourteen asymptomatic subjects with serum cholesterol larger than or equal to 350 mg/100 ml and/or TG larger than or equal to 3.50 mmol/l in the screening test but without signs or symptoms of secondary hyperlipideaemia or history of cardiovascular disease were examined further. 3. LP analysis with preparative ultracentrifugation separating very lof cholestrol and TG concentrations in each fraction was performed. LP paper electrophoresis was run on while serum and on top and bottom fractions after separation in the ultracentrifuge at d=1.006. Typing of hyperlipoproteinaemia (HLP) was performed according to WO based upon the values of for VLDL and LDL. Exercise ECG was performed on a heart rate controlled bicycle ergometer. The subjects worked at constant predetermined heart rates. ECG at rest and furing exercise was interpreted without knowledge of whether or not the subject has HLP and coded according to the Minnesota criteria. Digital pulse plethysmography was performed on the lower limbs....