This dissertation research comprised three studies examining the effects of acute and chronic endurance exercise on circulating angiogenic cells (CACs). Because the balance between nitric oxide (NO) and reactive oxygen species (ROS) is a critical aspect of the physiological function/dysfunction of CACs, each study determined the effects of exercise on NO-ROS balance within a variety of CAC types. Study #1 demonstrated that regular endurance exercise is associated with greater basal intracellular NO levels in cultured CACs, and that one mechanism underlying this association was increased NADPH oxidase enzyme activity in the sedentary state. Study #2 suggested an association between a sedentary lifestyle and increased nitro-oxidative stress in freshly-isolated CD34 ⁺ progenitor cells. Study #3 demonstrated that prior exercise attenuates high-fat meal induced-increases in mitochondrial-derived intracellular ROS in CD31⁺ CACs. Overall, it is concluded that acute and chronic endurance exercise enhance intracellular NO and ROS dynamics in CACs.