Infiltrating the operative site prior to incision with an epinephrine solution will provide vasoconstriction and a dryer operative field. However, some surgeons fear that as the vasoconstrictive effects of the epinephrine subside, smaller vessels will rebleed and a hematoma may result. In this study, 51 rats were operated with two flaps. The ventral pedicled flap, based on the inferior superficial epigastric arteries, and the McFarlane dorsal skin flap were utilized. The perimeter of all flaps was infiltrated with one of the following test infusions: (1) no infiltrate (control group), (2) 1% lidocaine hydrochloric acid (HCI), (3) 2% Iidocaine HCI, (4) 1% Iidocaine HCI and epinephrine 1:100,000, and (5) 0.5% Iidocaine HCI and epinephrine 1:200,000. Flaps were replaced In their beds. Animals were sacrificed 24 hours postoperatively. Flaps were raised at 26 hours and the coagulum weighed. No statistically significant difference was found between the weights of the coagulum of the infiltrated flaps versus the noninfiltrated flaps. Statistical power calculations on the main study flap yielded values greater than 80%. This suggests that the difference in delayed bleeding between noninfiltrated flaps and flaps infiltrated with various combinations of Iidocaine and epinephrine was insignificant.