Haemodynamic and metabolic effects of glucose-potassium-insulin (GKI) were studied in 14 patients with peritonitis. Study entry criteria were: hypodynamic septic shock (mean arterial pressure less than 50 mmHg and cardiac index less than 3.5 l/min) despite a highly positive fluid balance (greater than +2,000 ml during the last 12 h) and use of catecholamines (greater than 15 mcg/kg/min Dobutamine). GKI (glucose 70% 1 g/kg + potassium 10 mval + insulin 1.5 U/kg) was infused within 15 min via a central venous catheter. Before and 10 min after GKI haemodynamic and metabolic measurements were performed. GKI led to significant increases in systolic (+53%) and mean (+61%) arterial pressures, cardiac index (+50%), right (+60%) and left (+109%) ventricular stroke work indices, and oxygen consumption index (+18%). Heart rate remained unchanged, pulmonary shunt fraction increased slightly, systemic and pulmonary vascular resistances showed an insignificant decline. Serum glucose (p less than 0.01) and pCO2 (p less than 0.1) increased. The haemodynamic improvement lasted from 30 min or less (n = 3; 21%) to several hours. Nine patients (64%) survived more than 2 days, and two patients (14%) were eventually discharged from the hospital. We conclude, that in hypodynamic septic shock refractory to volume loading and catecholamine treatment GKI may be beneficial, although the mechanism of action remains unclear.