Fasting serum cholesterol and triglyceride levels, and lipoprotein electrophoretic patterns have been investigated in 42 men aged 67-92 years (mean 79 years). Although all the cholesterol and the majority of the triglyceride levels were within the normal range for younger people, both were significantly greater (P < 0.001 and P < 0.01 respectively) in old men who had a clinical history of ischaemic heart disease than in the aged controls, whereas, in patients with dysrhythmia-ischaemia the cholesterol levels were raised (P < 0.05) but not the triglycerides. An abnormality of liporpotein profile was observed in 58% of patients with ischaemic heart disease; 7% of the controls; and 20% of patients having myocardial ischaemia associated with supraventricular dysrhythmia.