BACKGROUND The magnitude and duration of the serum triacylglycerol response to a fatty meal may be predictive of coronary artery disease. Exercise can modify this aspect of cardiovascular risk but the effective intensity, duration and timing of exercise is uncertain. METHODS The influence of a single period of walking on the lipaemic response to a high-fat meal (1.2g fat and 71 kj per kilogram body mass) was examined in 12 normolipidaemic young adults (aged 21-33 years, six men and six women). The meal was ingested on two different occasions in a balanced, crossover design. In the control phase, participants rested for 6 h after consuming the meal; in the exercise phase, they walked on a treadmill for 1.5 h at 40% of their maximal oxygen uptake, starting 1.5 h after the meal, and then rested for a further 3 h. Lipid and lipoprotein levels were measured in venous blood taken during the fasted state and at intervals for 6 h after the meal. CONCLUSIONS The area under the triacylglycerol-time curve was 24 +/- 11% lower during the exercise phase (P < 0.05) than during the control phase because serum triacylglycerol concentrations were lower during recovery from exercise, 3-6 h after the meal. CONCLUSIONS Prolonged walking starting 1.5 h after the consumption of a fatty meal attenuates postprandial lipaemia in normolipidaemic young adults.