The omentum used as a vascular carrier is a new experimental model for prefabrication of free flaps in the rat. A 2.5 x 4 cm patch of omentum with gastroepiploic vessels and its rich vascular arcades was transferred under a bipedicled 2.5 x 6 cm right abdominal panniculocutaneous flap. At subsequent time intervals (postoperative days 0, 3, 5, 7, and 14), the skin pedicles were divided and the skin flap was raised as a composite island flap vascularized only by the underlying omental patch. The composite flap was then sutured back in place. Prefabricated flaps examined postoperatively demonstrated a dye fluorescence index (DFI) of 4.60% +/- 2.82% and 1.67% +/- 4.08% flap survival (FS) in the day 0 group; in the day 3 group, 9.83% +/- 1.47% of DFI and 15.00% +/- 10.35% of FS; in the day 5 group, 28.39% +/- 5.25% of DFI and 86.0% +/- 12.74% of FS (P less than 0.05); in the day 7 group, 38.19% +/- 7.52% of DFI and 98.13% +/- 3.72% of FS (P less than 0.05); and, in the day 14 group, 49.55% +/- 6.70% of DFI and 100% of FS (P less than 0.05). India-ink injection and histologic examination confirmed revascularization of the overlying skin by day 5.