Nine patients with intermittent claudication diagnosed at least 6 months before this investigation were evaluated to determine the effects of walking exercise on serum lactate accumulation (HLa, mmol⁻¹), ankle pressure index (API), total treadmill time (sec), and onset of leg pain (sec) in the most severely diseased limb. Subjects were evaluated via a functional walking tolerance test before participation in a thrice-weekly exercise program lasting 6 weeks. Post- treatment, the participants were re-evaluated on an identical walking test. Measurements of HLa accumulation and API were taken at rest and immediately following termination of the treadmill test. In the training sessions, body weight (kg), exercise heart rate (HR), systolic blood pressure (SBP), and distance traveled (m) were recorded daily. There were no significant changes (p<.05) after training in total time (mean increase = 23.7%) or time for onset of pain in the treadmill test (mean increase = 30.1%). Neither were there significant changes (p<.05) in API or HLa levels taken immediately after exercise, when pre- and post-training treadmill test data were compared. The weekly responses for exercise HR, and SBP, as well as body weight remained stable throughout. Mean distance walked by the subjects increased 203% (± 45%) across the 6 weeks. These data suggest that increases in total distance walked in an exercise program were apparently not related to HLa accumulation or API measurements in the working muscles, and that other mechanisms must be investigated in future studies to explain enhanced performance of such subjects.