The effects of walking training on VO2max, serum lipoproteins and plasma fibrinogen were studied in 119 healthy middle-aged persons. Training prescription was 65-75% of VO2max, 50 min/session, four times a week for 15 weeks. The net difference (between pre-posttraining changes in the walking and control group) was statistically significant for VO2max (0.14 l .min-1, 95% CI 0.04, 0.23), total cholesterol (-0.20 mmol.l-1, CI -0.34, -0.06), LDL cholesterol (-0.17 mmol.l-1, CI -0.29, -0.05), ratio of HDL cholesterol to total cholesterol (0.014, CI 0.005, 0.023), and triglycerides (-0.15 mmol.l-1, CI -0.26, -0.04). No statistically significant changes occurred in fibrinogen. The findings indicate that walking training of moderate intensity resulted in a modest increase in VO2max and minor but consistently favorable changes in serum lipoproteins.