Even with excellent operative techniques, prolonged ischemic periods may cause unwanted results because of a complex mechanism called reperfusion injury. Various pharmacological and immunological agents have been used to prevent this type of injury. Another known way to diminish reperfusion injury is the gradual reperfusion of the ischemic tissues. In this study, the effect of a gradual increase in blood flow on ischemia-reperfusion injury of the skeletal muscle was investigated. The right hind limbs of 15 rats were partially amputated, leaving the femoral vessels intact. Preischemic femoral arterial blood flow was measured by using a transonic small-animal blood flowmeter (T106) in all animals. The rats were divided into three groups: Group I consisted of control rats; no ischemia was induced. Group II was the conventional clamp release group. Clamps were applied to the femoral vessels to induce 150 minutes of ischemia. The clamps were then released immediately and postischemic blood flow was measured. Group III was the gradual clamp release group. After 150 minutes of ischemia, clamps were released gradually at a rate so that the blood flow velocity would reach one fourth the mean preischemic value at 30 seconds, one half at 60 seconds, three fourths at 90 seconds, and would reach its preischemic value at 120 seconds. Total clamp release was allowed when blood flow was less than 1.5 fold of the preischemic values. Postoperatively the soleus muscles were evaluated histopathologically, and malonyldialdehyde and myeloperoxidase levels were measured. The mean preischemic blood flow was 13.6 +/- 2.24 ml per kilogram per minute in all groups. In the conventional release group, postischemic flow reached four to five fold its preischemic values (61.06 ml per kilogram per minute). Histopathology revealed more tissue damage in the conventional release group. Malondialdehyde and myeloperoxidase levels were also significantly lower in the gradual release group. Depending on histological and biochemical findings, a gradual increase in blood flow was demonstrated to reduce the intensity of ischemia-reperfusion injury in the soleus muscle of this animal model.