These studies were undertaken to determine if perfusion fluorometry can provide an accurate, reliable means of monitoring neovascularization and predicting optimal time of flap division. An animal model was developed that permitted daily assessment of neovascularization of the flap using fluorescein injections and the fluorometer. An increase in fluorescence of the pedicle-occluded flap of approximately 12 percent the normal skin fluorescence was associated with 100 percent flap survival. This occurred after only 4 days in the rat. Fluorometry proved valuable in the evaluation of clinical flaps. The fluorescence of flaps during pedicle occlusion was observed to increase with each successive fluorometric evaluation performed at 3- to 7-day intervals. It appears that flaps after pedicle occlusion exhibiting at least 25 percent of the fluorescence of normal skin will tolerate pedicle division. Based on the neovascularization studies of the clinical flaps, all pedicles were severed earlier than originally anticipated. Two cross-leg flaps were successfully divided after 11 days. Quantitative assessment of serial fluorescein injections allows reliable evaluation of neovascularization in clinical interpolation flaps and is useful in the timing of flap division.