The manuscript deals with the effects exerted by the inflammatory microenvironment on angiogenic cell expansion and arterial specification. Data reported demonstrated that the inflammatory cytokine IL-3 expands a subset of hemopoietic-derived cells, which directly contribute to neovessel formation. In addition, the identification of STAT5 as a molecular signature of the vasculogenetic process provides the rationale for a novel therapeutic strategy to manipulate vascular growth.