The aims of this study were to investigate the interrelationships between endothelial progenitor cells (EPCs), peripheral arterial disease (PAD), and atherosclerotic risk factors, as only limited data are available regarding the EPCs in patients with PAD. The authors studied the number of EPCs by different methods in a carefully selected group of 45 patients with PAD along with 24 healthy subjects (HS). In patients with PAD, by utilizing the dual-binding method, the number of EPCs was significantly increased compared to HS (M +/- SD, PAD: 73 +/- 33, HS: 52 +/- 20 EPCs/high power field; p < .001). On the contrary, both CD34(+) cell count and CD133(+) cell count were significantly decreased compared to HS. Colony-forming units were significantly increased in PAD compared to HS (median and 25th and 75th percentiles, PAD: 7, 1, 9; HS: 1, 1, 4 CFU/well, respectively; Mann-Whitney, p = .006). In patients with PAD, the number and proliferative activity of circulating EPCs are increased with respect to HS even though EPC count by flourecence-activated cell sorting (FACS) analysis provided different results and this may explain the discrepancy in data collected using different methods. The regulation of the number and biological activity of EPCs in PAD remains unclear.