Fms-like tyrosine kinase 1 (Flt-1), also known as vascular endothelial growth factor receptor 1 (VEGFR1), is a transmembrane tyrosine receptor kinase that is highly expressed in vascular endothelial cells. VEGF/Flt-1 transduced signaling is required for the recruitment of haematopoietic precursors and endothelial cell progenitors, migration of monocytes and macrophages, and release of growth factors from hepatic endothelial cells. Induction of Flt-1 signaling has been implicated in tumor metastasis. The Human Flt-1 Kit provides the assay-specific components for the quantitative determination of Flt-1 in human serum, plasma, cell supernatant, cerebral spinal fluid, urine, and cell lysate.