Post-prandial hypertriglyceridaemia is associated with ischaemic heart disease although the mechanism linking both is uncertain. To determine if measures of insulin resistance, insulin secretion and post-prandial changes in non esterified fatty acid concentration were associated with post-prandial hypertriglyceridaemia, 57 previously healthy Caucasian men between the ages of 57 and 70 years, underwent an OGTT and an 8h fat tolerance test. Post-prandial plasma NEFA concentration was associated with triglyceride-rich lipoprotein concentration (TGRLP-density<1.006g/ml, comprised largely of chylomicrons) (r=0.33, p=0.01) and with VLDL concentration (r=0.37, p=0.01). Neither fasting insulin, nor 30 minute insulin increment (as measures of insulin resistance and insulin secretion respectively) were associated with post-prandial hypertriglyceridaemia. There was no difference in the post-prandial triglyceride response between current smokers and life-long non smokers. In conclusion these results suggest that the post-prandial rise in NEFA concentrations occurs and a result of lipolysis of triglyceride-rich lipoproteins and the post-prandial increase in NEFA concentrations causes increased VLDL production.