This study, using 62 rabbits, examines the rate and pattern of vascular outgrowth from a subcutaneously implanted vascular pedicle, how the newly formed vessels connect to preexisting skin vessels, and whether local application of basic fibroblast growth factor can accelerate the angiogenic process. When the femoral artery and vein of rabbits are implanted beneath the skin, angiogenesis from both the pedicle and small blood vessels within the adjacent skin begins within 3 days. Perfusion with India ink reveals connections between the pedicle and dermal vessels as early as 5 days after implantation of the pedicle. Provided the pedicle does not thrombose, skin flaps based on it may survive completely when elevated as early as 2 weeks after implantation. Flap survival depends on the development of a small number of vascular connections between vessels arising from the pedicle and preexisting dermal vessels. If elevation is delayed until 4 weeks after implantation a flap may survive even if its pedicle has thrombosed. Prolonged release of basic fibroblast growth factor adjacent to the pedicle significantly increases the survival of flaps elevated 1 week after implantation but does not alter the survival of flaps elevated at 2 and 4 weeks.