This study was conducted to determine the hemodynamic response to uncontrolled hemorrhage following aortotomy in anesthetized swine. Eight Yorkshire swine underwent splenectomy and stainless steel wire placement in the anterior infrarenal aorta and were instrumented with Swan-Ganz and carotid artery catheters. Following an equilibration period, the wire was pulled. This produced a 5 mm aortotomy and spontaneous intraperitoneal hemorrhage. Serial measurements of mean arterial pressure (MAP), mean pulmonary artery pressure (MPAP), and cardiac output (CO) were obtained. From baseline to 5 min after aortotomy, there was a profound decrease in MAP in conjunction with a significant decrease in CO and MPAP. After the initial 5 min period, there was a progressive elevation in MAP, CO, and MPAP. Peripheral vascular resistance (PVR) was significantly decreased after aortotomy and returned to baseline after 60 min. From these data, we conclude that aortotomy produces a rapid depression and spontaneous recovery in MAP, CO, and MPAP. Aortotomy also produces a significant decrease in PVR, which is not generally associated with hemorrhagic hypotension.