The erythropoietin receptor (EPOR) is a member of the cytokine receptor family. There are several isoforms including: EPOR-F (full length), EPOR-S (soluble form), and EPOR-T (truncated form). Upon erythropoietin (EPO) binding, the EPOR activates Jak2 tyrosine kinase which activates different intracellular pathways including: Ras/MAP kinase, phosphatidylinositol 3-kinase and STAT transcription factors. The stimulated EPOR appears to have a role in erythroid cell survival. Defects in the EPOR may produce erythroleukemia and familial erythrocytosis. A functional EPOR is found in the cardiovascular system, including endothelial cells and cardiomyocytes, and data suggest that the EPO/EPO receptor system plays an important role in cardiac function. In animal studies, treatment with EPO during ischemia/reperfusion in the heart has been shown to limit the infarct size and the extent of apoptosis.