This study was designed to evaluate the effect of different wound environments on wound activation. Our wound model provided two distinct environments, a well vascularized musculocutaneous flap and a poorly perfused random-pattern flap, in miniature swine. Leukocytes were isolated and analyzed by the following three variables: surface and total cellular Mac-1 (CD11b/CD18), superoxide anion expression, and lactoferrin release. Leukocytes from the unfavorable, poorly oxygenated wound environment activate on entry into the wound. Leukocytes from the musculocutaneous flap wound are better able to respond to a maximal challenge with the phorbol ester, phorbol myristate acetate. These findings may account for the enhanced bactericidal actions of the musculocutaneous flap compared with the random-pattern flap observed clinically.