Large island skin flaps, comprising the entire abdominal covering in rats, were raised on one neurovascular pedicle in the groin. A standard area of necrosis was produced on the other side from the pedicle. However, when the animals were treated with certain vasodilator drugs for 15 days before and 7 days after the flaps were raised, there was little or no necrosis. The effect of the drug therapy was the same as a surgical delay.