Adiponectin was revealed to have anti-atherogenic and anti-inflammatory properties and has been recently found to stimulate angiogenesis in vivo and in vitro. However, the role of adiponectin in endothelial differentiation remains unclear. The objective of this study was to investigate whether adiponectin can promote peripheral CD14(+) monocytes differentiation into endothelial cells (ECs). Human peripheral blood CD14(+) monocytes were cultured with or without adiponectin (10 microg/ml) for 10 days. Adiponectin significantly promoted EC morphology formation from CD14(+) monocytes. By flow cytometery analysis, cells treated with adiponection substantially increased mean fluorescence intensity of vascular endothelial growth factor receptor-2 (VEGFR-2) and endothelial nitric oxide synthase (eNOS), two specific endothelial markers, by 49.2 % and 53.9 %, respectively, as compared to control cells. By real time PCR analysis, the mRNA level of eNOS in adiponectin-treated cells was also increased by 31.9 % of that of the control cells. However, the mRNA levels of calponin and SMMHC, two specific SMC markers, in adiponectin-treated cells were decreased by 81.1 % and 79.7 % of that of the control cells, respectively. These data demonstrated that adiponectin could promote endothelial differentiation from peripheral blood CD14(+) monocytes by morphology change, upregulation of EC markers and downregulation of SMC markers. Adiponectin-promoted EC differentiation may contribute to vascular healing and angiogenesis.