A single bout of exercise has been shown to positively alter blood lipids in healthy, non-smoking men. However, since cigarette smoking negatively alters blood lipids, the positive effects of exercise on blood lipid has not been documented. PURPOSE: Examine the effects of treadmill walking to expend 600kcal at 65% VO2peak on the blood lipids of male cigarette smokers (≥10 cigarettes/day for ≥6months). METHODS: Five cigarette smokers (SMK) who were 21±2yrs old, 76.9±9.3kg in weight, 1.8±0.1m tall, 14.3±5.1% body fat and had a VO2peak of 44.4±0.9ml/kg/min and five non-smokers (NS) who were 23±2yrs old, 89.5±13.9kg in weight, 1.8±0.1m tall, 19.9±5.2% body fat and had a VO2peak of 42.6±2.0ml/kg/min volunteered for this study. Each subject randomly completed two trials: a no exercise control trial (CON) and a 600kcal treadmill walk at 65% VO2peak (EXER). Body composition was determined with air plethysmography and VO2peak with open-circuit spirometry utilizing the Bruce treadmill protocol. Veni puncture was performed at baseline, 24, and 48hrs post-exercise of each trial for collection of fasting blood for the determination of lipids and LDL particle size. SMK continued to smoke on their regular schedules, but had ≥1 cigarette w/in one hour of each sampling period. RESULTS: There were no group differences in descriptive data. Additionally, there were no differences between baseline CON and EXER data, nor in data over CON trial within each group. There were no differences in total cholesterol (TC), HDL-C, HDL3-C or LDL particle size between groups at baseline EXER. NS had higher HDL2-C (15.0±1.8 vs 7.6±5.3mg/dL) and lower triglycerides (TG; 84.6±10.9 vs 114.0±25.6mg/ dL) as compared to SMK at baseline EXER. HDL-C increased at 24hrs post-exercise by 7.6% (46.0±3.6 to 49.8±3.9mg/dL) in NS, and 10.1% (43.4±5.3 to 48.3±6.1mg/dL) in SMK. HDL2-C increased 18.5% (15.0±1.8 to 18.4±2.6mg/dL) in NS, and 50.0% (7.6±5.3 to 15.2±8.4mg/dL) in SMK. TG decreased at 24hrs post-exercise by 20.0% (84.6±10.9 to 70.5±9.3mg/dL) in NS, and 72% (114.0±25.6 to 66.1±24.0mg/dL) in SMK. There were no differences between NS or SMK in the absolute magnitude of change in HDL-C, HDL2-C and TG over EXER. TC, HDL3-C, nor LDL particle size was altered over EXER. CONCLUSION: An acute bout of walking at 65% VO2peak which expended 600kcal was sufficient to favorably modify HDL-C, HDL2-C and TG in these men, but did not impact TC, HDL3-C, or LDL particle size. These results suggest that the negative effects of cigarette smoking did not interfere with the positive effects of an acute bout of walking on blood lipids.