The present article summarizes recent data presented at the Exercise and Hemorheology symposium during the 15th Conference of the European Society for Clinical Hemorheology and Microcirculation (June 28-July 1, Pontresina, Switzerland, 2009). The review starts with several unresolved paradoxes in exercise hemorheology. Then, we focus on the potential hemorheological and immunological mechanisms involved in the adverse events sometimes reported in exercising sickle cell trait carriers, and the role of habitual physical activity. In a fourth part, new results on the effects of acute hypoxia on blood rheology are presented. Finally, we will discuss recent experimental evidences on the role of exercise on the regulation of nitric oxide synthesizing mechanisms in red blood cell.