In 16 patients with necrotizing pancreatitis and in 6 patients with edematous-interstitial pancreatitis, hemodynamic studies were conducted between the first and the 12th day after the onset of illness. Patients with necrotizing pancreatitis had a high cardiac index of 4.47 +/- 0.75 L/min X m2 and a low total peripheral vascular resistance of 884 +/- 180 dyn X s/cm5, a low mean pulmonary vascular resistance of 84.3 +/- 25.7 dyn X s/cm5, and a high pulmonary shunt fraction of 24.2% +/- 6.6% of the cardiac output. This hyperdynamic vascular pattern was not found in patients with edematous-interstitial pancreatitis associated with gallstone disease. The group of patients with edematous-interstitial pancreatitis had a cardiac index of 3.21 +/- 0.8 L/min X m2, a total peripheral vascular resistance of 1337.8 +/- 248.2 dyn X s/cm5, a mean pulmonary vascular resistance of 130.7 +/- 48.2 dyn X s/cm5, and a pulmonary shunt fraction of 13.6% +/- 3.5% of the cardiac output. There was a significant difference between the patients with necrotizing pancreatitis and those with edematous-interstitial pancreatitis in the following hemodynamic parameters: heart rate (p less than 0.02), cardiac index (p less than 0.01), total peripheral vascular resistance (p less than 0.001), arteriovenous oxygen difference (p less than 0.02), and pulmonary shunt fraction (p less than 0.01). These findings in patients with necrotizing pancreatitis demonstrate an opening of intrapulmonary shunts and peripheral vasodilatation probably due to the release of pancreatitis-associated toxic agents in the early phase of the disease.