In a prospective study, we documented the hemodynamic effects of conventional donor maintenance in 24 brain-dead organ donors. Patients were then randomized to receive either saline or a low dose arginine vasopressin (AVP) infusion. In the AVP group (n = 11), plasma hyperosmolality decreased (P < 0.05), blood pressure increased (P < 0.01), inotrope use decreased (P < 0.01), and cardiac output was maintained. In the control group (n = 13), plasma hyperosmolality increased (NS); no significant change in blood pressure, cardiac output, or inotrope infusion rate occurred. Myocardial ATP levels were higher in the AVP than the control group (NS). Early organ function was similar in the 2 groups. We conclude that the use of a low dose AVP infusion enables inotrope use to be reduced and recommend consideration be given to the use of a low dose AVP infusion in potential thoracic organ donors.