Increased postprandial lipemia has been stated as one of the mechanisms responsible for atherogenesis in smokers. We measured the postalimentary lipid response and the in vivo intravascular delipidation index of an artificial chylomicron emulsion in healthy adult smokers and controls. The blood was collected in the fasting state immediately after the smokers smoked one cigarette. The lipemia was measured 2, 4, 6 and 8 h postalimentarily in smokers (S, n = 8) and in non-smoking controls (C, n = 8) and the chylomicron metabolism rate was measured 2, 4, 6, 8, 12, 16, 20, 24 and 30 min after the injection of an artificial emulsion to S (n = 10) and to C (n = 10). The lipoproteins were isolated in the fasting period and 4 h after the fatty meal and their chemical composition in cholesterol, triglycerides, phospholipids and protein was determined. Smokers showed an increased lipolysis percentage value (mean +/- S.E.M.) of the artificial chylomicron (39.1 +/- 3.1) compared to controls (26.5 +/- 3.3) and higher levels of HDL(2)-PL: 28.4 +/- 4.3 (S) versus 16.2 +/- 2.0 (C) mg/dl (mean +/- S.E.M.). In conclusion, the oral fat tolerance was not altered in smokers but an upregulation of the rate of metabolism of the TG-rich lipoproteins was elicited immediately after smoking one cigarette.