The current study in rats concerns two aspects of the flap/bed interaction: fluorescein kinetics and histological finding. In the control group of animals in the fluorescein kinetics experiment, flaps were raised and then reattached. In one experimental group, the flaps were raised and placed on a sterile polyethylene film. In two other groups, the flaps were raised and then the pedicle was cut, either immediately or at specific intervals. At intervals up to 24 hours several animals were injected with 5% fluorescein. In the control group fluorescein penetration increased with time, while it decreased in the polyethylene-film group. There was virtually no fluorescein staining in both cut-pedicle groups. To study histological events, the animals were divided into groups with flaps and groups in which the distal end of each flap was severed to form a contiguous skin graft. Other conditions were varied. All flaps were cultured, and biopsy specimens were obtained from three areas at several time intervals. Histological sections from the distal flap were markedly different from the corresponding skin grafts. These results corroborate previously noted survival rates.