A severe microarterial trauma (arteriotomy/intimectomy) was introduced to the central arteries of rabbit ears. Twenty-one patent vessels, 3 at each interval of 2 hours, 1, 3, 7, 14, 30, and 90 days after reperfusion were taken for light and scanning electron microscopy studies. These vessels remained patent at all time intervals. A physiological "in vivo" perfusion technique with fixation fluid of normal temperature (37 degrees C), pressure (120 mm Hg) and osmolarity (300 mOsm) was used to ensure fixed relaxed vessels. The endothelial, internal elastic, and part of the medial layers of vessel walls were removed following intimectomy. The inner surface of the intimectomy region was irregular and partly covered with thrombotic materials between 2 hours and 3 days postreperfusion. Endothelialization of the traumatized region was first observed at 3 days and was completed between 7 and 14 days. Intimal hyperplasia developed during this period and had not diminished in thickness by 30 or 90 days. The trauma and healing process of the arteriotomy/intimectomy are similar to the healing of vascular anastomoses and virtually identical to the clinical trauma of vessel avulsion, but neointima formation is more pronounced and engages vessel walls far outside the intimectomy site.