The cardiovascular effects of the mycotoxin fumonisin were examined in male cross-bred pigs fed 20 mg/kg of fumonisin-containing culture material for 7 days. On Day 8, pigs were anesthetized with halothane and surgically catheterized. Cardiovascular measurements and blood gas analyses were obtained during halothane anesthesia and 18 hr after recovery from anesthesia. Pigs fed fumonisin had significant (p < 0.05) decreases in maximal rate of change of left ventricular pressure, heart rate, cardiac output, and mean aortic pressure, a significant increase in mean pulmonary artery pressure and pulmonary vascular resistance, and no change in left ventricular end-diastolic pressure, pulmonary wedge pressure, and central venous pressure. Treated pigs also had significant decreases in both arterial and mixed venous blood O2 tension, and systemic oxygen delivery, but significantly increased oxygen consumption and oxygen extraction ratio. These results suggest that fumonisin increases oxygen consumption and is a negative inotropic and chronotropic agent in pigs. Because fumonisin is a naturally occurring inhibitor of the enzyme sphingosine N-acyltransferase, thereby increasing sphingosine concentrations in vivo, we speculate that the observed cardiovascular effects were mediated in part by a fumonisin-induced increase in tissue sphingosine concentrations.