Abstract. Neuregulin-1 (NRG-1) is a positive regulator of angiogenesis, which suggests there may be an association between NRG-1 and angiogenic factors. The aim of the present study was to investigate the effect of treating human cardiac microvascular endothelial cells (HCMECs) with angiogenic factors on NRG-1 expression and secretion. HCMECs were cultured and stimulated with vascular endothelial growth factor (VEGF; 100 ng/ml), angiopoietin (Ang)-1 (100 ng/ml) or Ang-2 (100 ng/ml) under normal or hypoxia/serum deprivation (Hypo/SD) conditions for 24 h. The expression of ErbB receptors and NRG-1 in HCMECs was measured by western blot analysis and the secretion of NRG-1 in HCMECs was determined by ELISA. The results demonstrated that ErbB2, ErbB3 and ErbB4 were expressed in HCMECs and that ErbB2 expression levels were notably higher than those of ErbB3 and ErbB4. Under normal culture conditions the expression and secretion of NRG