Objective To investigate the proliferation of rat bone marrow endothelial progenitor cells (EPCs) in the culture under different concentrations of TGF-?1 in order to optimize the culture conditions. Methods EPCs harvested from bone marrow by flushing fresh rat femur and tibia were isolated by density gradient centrifugation. The isolated cells were further purified and enriched by fast adhere to fibronectin coated dish. Flow cytometry was applied to enrich the cells positive to CD34, CD133 and VEGFR-2. EPCs were expanded in M199 medium in presence of different concentrations of TGF-?1 (10-300 pg/ml). Total cell output was recorded; and the expressions of CD34, CD133, and VEGFR-2 at different cell passages were analyzed through flow cytometer. Results Fast adhere cell group showed significantly higher positive proportion of CD34, CD133, and VEGFR-2 than unsorted cells (P