Microparticles (MPs) are small membrane vesicles shed from plasma membranes following cell activation or apoptosis. They are released from a variety of cells including endothelial cells, smooth muscle cells, platelets, leukocytes, and erythrocytes. MPs are produced in a healthy state, however changes in the number and composition of MPs are associated with many disease states, including cardiovascular disease (CVD), venous thrombosis, diabetes mellitus, rheumatic disease and other inflammatory states. MPs may be used as a marker of dysfunction in many of these disease states. Exercise has been shown to have a positive effect on many of these disease states with MPs a possible biomarker of improvement. Study 1: This study examined the effect of isocaloric bouts of exercise at 60%, 70% and 80% V̇O2max on circulating levels of MPs in healthy young men. There was a significant increase in mean numbers of circulating endothelial MPs (EMPs) 6 h following each bout. Compared to baseline circulating platelet MPs (PMPs) did not increase during any of the acute bouts of exercise. Study 2: This study examined the effect of 14 consecutive days of aerobic exercise on circulating MPs. There was no difference in circulating EMPs before exercise, immediately after exercise and 13 h following exercise on day 1, 3, 7, 10 and 14 of the training program. Circulating EMPs were significantly decreased 13 h following training compared to immediately post training. There were no changes in platelet MP numbers. There was no correlation between aerobic fitness and circulating MP numbers Study 3: This study examined the effect of 4 weeks of low-volume, short duration high-intensity interval training (LS-HIIT) and cardiac rehabilitation on circulating MPs in individuals with CVD. There were no changes in MP numbers in either group following the exercise intervention. Flow-mediated dilation was significantly higher in the LS-HIIT group than the cardiac rehabilitation group following the exercise intervention Conclusions: EMPs increase following an acute bout of isocaloric exercise at 60%, 70% and 80% V̇O2max in healthy young trained men. Aerobic exercise training for 14 consecutive days elicits a significant increase in aerobic fitness. Circulating EMPs decrease 13 h following training. Endothelial function is significantly improved and circulating MPs are unchanged in men and women with CVD following 8 sessions of LS-HIIT. There were no changes in circulating PMP numbers in response to acute or chronic exercise.