The purposes of this study were to determine the relationship between the physical activity values obtained from the peripheral arterial disease-physical activity recall (PAD-PAR) questionnaire and (1) the free-living daily physical activity obtained from the doubly labeled water technique and (2) clinical measures of PAD severity. Fifty-one older PAD patients (age= 70 +/- 6 years) were recruited from the Vascular Clinic at the Baltimore Veterans Affairs Medical Center and from radio and newspaper advertisements. Energy expenditure of physical activity (EEPA) was determined by using doubly labeled water and indirect calorimetry techniques. PAD severity was measured by ankle/brachial index (ABI) and walking distance to maximal claudication pain determined during a graded treadmill test. In addition, patients were also characterized on body composition and total daily energy expenditure. The physical activity values obtained from the PAD-PAR questionnaire (113 +/- 37 MET-hr/wk) were not related to EEPA (542 +/- 260 kcal/day; r= -0.057, p=0.690), ABI (0.64 +/- 0.19; r=0.032, p=0.826), or distance to maximal claudication pain (376 +/- 229 m; r=-0.054, p=0.731). The authors conclude that the PAD-PAR questionnaire is not an accurate measurement of free-living daily physical activity when compared to EEPA by use of the criterion method of doubly labeled water, and the activity questionnaire measures were poorly correlated with clinical measures of PAD severity.