Traditionally, the tunica adventitia has been regarded as loose connective tissue, which was composed of fibroblasts, inflammatory cells, vasa vasorum, nerve endings and so on. It mainly functioned as supportive tissue and supplied nutrition to the vessel wall. Recently, accumulating data suggested that stem/progenitor cells were present in the adventitia. Under pathological conditions, resident stem/progenitor cells in the adventitia could differentiate into endothelial cells or smooth muscle cells, which were involved in atherosclerosis, vascular repair and remolding. This article briefly reviews the research status and advancement of stem/progenitors in adventitia.