We seeded tissue engineered human skin substitutes with endothelial cells (EC) differentiated in vitro from progenitors from umbilical cord blood (CB‐EC) or adult peripheral blood (AB‐EC), comparing the results to previous work using cultured human umbilical vein EC (HUVEC) with or without Bcl‐2 transduction. Vascularized skin substitutes were prepared by seeding Bcl‐2‐transduced or nontrans‐duced HUVEC, CB‐EC, or AB‐EC on the deep surface of decellularized human dermis following keratinocyte coverage of the epidermal surface. These skin substitutes were transplanted onto C.B‐17 SCID/beige mice receiving systemic rapamycin or vehicle control and were analyzed 21 d later. CB‐EC and Bcl‐2‐HUVEC formed more human EC‐lined vessels than AB‐EC or control HUVEC;CB‐EC, Bcl‐2‐HUVEC, and AB‐EC but not control HUVEC promoted ingrowth of mouse EC‐lined vessels. Bcl‐2 transduction increased the number of human and mouse EC‐lined vessels in grafts seeded with HUVEC but not with CB‐EC or AB‐EC. Both CB‐EC and AB‐EC‐induced microvessels became invested by smooth muscle cell‐specific alpha‐actin‐positive mural cells, indicative of maturation. Rapamycin inhibited ingrowth of mouse EC‐lined vessels but did not inhibit formation of human EC‐lined vessels. We conclude that EC differentiated from circulating progenitors can be utilized to vascularize human skin substitutes even in the setting of compromised host angiogenesis/vasculogenesis.—Shepherd, B. R., Enis, D. R., Wang, F., Suarez, Y., Pober, J. S., Schechner, J. S. Vascularization and engraftment of a human skin substitute using circulating progenitor cell‐derived endo‐thelial cells. FASEB J. 20, E1124–E1132 (2006)