Rationale: Mobilization and functions of endothelial progenitor cells (EPCs) are increased in acute myocardial infarction (AMI) patients. Yet, sleep disordered breathing (SDB) is highly prevalent in AMI patients. Objective: To compare EPCs numbers and functions in AMI patients with SDB (AMI-SDB) and without SDB (AMI-only) and to determine the effects of intermittent hypoxia (IH) in-vitro on EPCs proliferative and angiogenic properties. Methods: Forty male AMI patients underwent a whole-night sleep study using ambulatory monitoring. Nineteen had SDB (oxygen desaturation index >5 events/hour). AMI-SDB and AMI-only patients were matched by age, BMI, blood chemistry and co-morbidities. Blood samples were analyzed by flow cytometry, endothelial cell colony-forming-units (EC-CFUs), paracrine measures, blood chemistry, and oxidative stress, inflammatory and angiogenic markers. Effects of IH in-vitro were studied in twelve healthy subjects. Measurements and main results: Circulating EPCs (CD34+/ KDR+), angiogenic T cells (CD3+/CD31+/CXCR4+) and vascular endothelial growth factor (VEGF) in monocytes were significantly higher in AMI-SDB patients. Also, EC-CFUs numbers and EC-CFUs paracrine effects on endothelial tube formation were significantly higher in AMI-SDB then in AMI-only patients. Similarly, in cell cultures from healthy subjects, EC-CFUs numbers and their paracrine effects on endothelial tube formation were increased after exposure to IH in-vitro, compared to normoxia.Conclusions: Co-existent mild-moderate SDB in AMI patients increased the mobilization, proliferative and angiogenic capacities of EPCs, angiogenic T cells numbers and VEGF expression in monocytes, compared to AMI patients without SDB. IH in-vitro had similar effects on healthy EPCs functions.