The effects of retrograde perfusion pressure on the brain was experimentally investigated during profound hypothermic circulatory arrest. Fifteen adult mongrel dogs were placed cardiopulmonary bypass and induced profound hypothermia of 20 degrees C at nasopharyngeal temperature. Retrograde cerebral perfusion (RCP) with perfusion pressure of 10 mmHg (RCP10; n = 5), 20 mmHg (RCP20; n = 5), 30 mmHg (RCP30; n = 5) underwent for 60 minutes. The oxygenated blood was infused via the bilateral maxillary veins, and the flow rate was kept to maintain a desired pressure in the external jugular vein for each group. Regional cerebral blood flow (rCBF), excess lactate, cerebrospinal fluid pressure (CSFP), adenosine triphosphate (ATP) concentration of cerebral tissue, and water content of cerebral tissue were measured. In the RCP10 group, cerebral excess lactate was positive and ATP concentration was low. In the RCP30 group, the water content of cerebral tissue was significantly higher than those in the other groups. In the RCP20 group, the excess lactate was maintained in a negative range, and ATP concentration was significantly higher than in the RCP10 group. In conclusion, RCP may provide metabolically adequate support for the brain and a perfusion pressure of 20 mmHg was appropriate for RCP in dogs.