The purpose of this study was to compare calf muscle hemoglobin oxygen saturation response during exercise between smokers and non-smokers with peripheral arterial disease. Patients limited by intermittent claudication who were smokers (n = 12) were compared with those who had not smoked (n = 28) for at least 1 year prior to investigation. Ankle/brachial index (ABI) measurements were obtained with Doppler ultrasound, and maximal calf blood flow was measured by venous occlusion plethysmography. Hemoglobin oxygen saturation (StO2) of the calf muscle, initial claudication distance (ICD), and absolute claudication distance (ACD) were obtained during a graded treadmill test. Smokers refrained from smoking on the morning of the test. Smokers had similar ABI values compared with non-smokers (0.70 +/- 0.26 vs 0.73 +/- 0.23 [mean +/- SD]; p = 0.808), whereas the smokers had lower values for maximal calf blood flow (8.71 +/- 5.76 %/min vs 11.48 +/- 4.46 %/min; p = 0.038), ICD (122 +/- 123 m vs 243 +/- 177 m; p = 0.023), and ACD (284 +/- 170 m vs 452 +/- 263 m; p = 0.023). Additionally, smokers had lower calf muscle StO2 values at the end of 1 minute (16 +/- 15% vs 37 +/- 19%; p = 0.002) and 2 minutes of exercise (16 +/- 16% vs 35 +/- 25%; p = 0.008), and at the occurrence of ICD (17 +/- 17% vs 32 +/- 23%; p = 0.033) and ACD (16 +/- 16% vs 32 +/- 24%; p = 0.024). After adjusting for blood flow, calf muscle StO2 values remained lower in the smokers (p < 0.05). Finally, calf muscle StO2 at the end of the first minute of exercise was related to ICD (r = 0.611, p < 0.001) and ACD (r = 0.443, p < 0.01). In conclusion, smokers limited by intermittent claudication have lower calf muscle StO2 during exercise than nonsmokers, and lower StO2 during exercise is associated with shorter ICD and ACD.