The purpose of this study was to examine the influence of brisk walking on postprandial lipemia in 26 sedentary women aged 41 to 55 years. The lipemic response to a high-fat meal (mean +/- SEM: 73.8 +/- 1.3 g fat, 66% energy; 81.8 +/- 1.4 g carbohydrate) was determined pretraining and posttraining. Blood samples were obtained in the fasted state and hourly for 6 hours after the meal. Serum was analyzed for triacylglycerol (TAG), total cholesterol, high-density lipoprotein (HDL) and HDL2 cholesterol, apolipoproteins (apos) A-I and B, nonesterified fatty acids (NEFA), glucose, and insulin. Subjects were randomly assigned to one of two groups: walkers (n = 13) followed a program of brisk walking (average of 21 +/- 1 [range, 17 to 27] min.d-1 at 1.76 +/- 0.02 m.s-1), whereas controls (n = 13) maintained their habitual life-style. Procedures were repeated 12 weeks later, with 48 hours between the last training session and determination of postprandial lipemia. Eleven walkers and 13 controls completed the study. Responses over time were compared between groups (Mann-Whitney U, P < .05). Brisk walking improved endurance fitness and decreased body fatness, but had no influence on peak TAG concentration (walkers, 1.6 +/- 0.2 v 1.6 +/- 0.2 mmol.L-1; controls, 1.9 +/- 0.3 v 2.1 +/- 0.3) or the area under the TAG/time curve after the test meal. The area under the insulin/time curve decreased in walkers relative to controls. These results suggest that in sedentary women aged 41 to 55, brisk walking attenuates the serum insulin response, but not the lipemic response, to consumption of a high-fat mixed meal when these responses are determined 48 hours after the last exercise bout.