The role of leukocytes in the decreased perfusion following ischemia in skeletal muscle was examined in the microcirculation of the rat cremaster muscle. The isolated muscle was viewed with an intravital microscope. Diameters of A1 and A2 arterioles and collecting venules were determined hourly. The number of leukocytes rolling along the venular walls was determined from a videotape. Nonischemic (control) rats (n = 10) were observed for 6 hours. The ischemic group (n = 10) was observed for one hour, the iliac and femoral arteries and veins were then clamped for 4 hours, released, and the muscle was observed for another two hours. No change in arteriole or venule diameters occurred in the control group. The diameters of the arterioles in the ischemic group decreased significantly during reperfusion but, the venule diameters did not. There was a significant reduction during reperfusion but, perfused capillaries following ischemia compared to control. There was a small but not significant increase in the number of rolling leukocytes in the ischemic group. The extent of leukocyte rolling in postcapillary venules was found to not correlate with the decrease in capillary perfusion that occurs after ischemia and reperfusion. However, the decrease in capillary flow was associated with reduced arteriole diameters.