A new experimental skin-flap model is presented in which direct observations of blood flow in individual capillaries can be made from the time of flap creation throughout the entire evolution of the establishment of necrosis. After flap creation, one observes through the microscope that at 1 hour a large area of tissue is nonperfused as a result of the surgical trauma. This is followed by vasodilatation at 6 hours, resulting in an increase in the area of perfused tissue. At 24 hours, the vasodilatation persists, and the red cells that have entered the tissue during the vasodilatation (6 hours) accumulate in the capillaries, this being reflected by an increased area of nonperfused tissue. This increase continues to 72 hours, at which time the perfusion-nonperfusion interface becomes well defined and remains so throughout the 5-day experiment. Analyses of the relationship between early postoperative capillary perfusion and eventual necrosis are presented. Advantages and disadvantages of this model are listed.