Sedentary, eumenorrheic women (N = 27) 22 to 40 years of age, with high baseline levels of plasma high-density lipoprotein cholesterol, were randomly assigned to a walking (n = 16) or a control group (n = 11). The training program involved treadmill walking 4.8 km (3.0 miles) four times a week for 40 weeks at a mean intensity of 72% maximal heart rate. Aerobic power (VO2max) was improved by 22%, but no training effect was observed in body composition variables or blood lipid/lipoprotein levels. Despite additional increments in exercise intensity over the final 20 weeks of training, most of the improvement in VO2max was observed over the first 20 weeks of the study. Exercising subjects' baseline levels of plasma HDL-C were found to be inversely associated with the change (delta) scores in the lipoprotein (r = -0.51, p < or = .05).