Left ventricular performance was studied in 6 control and 7 experimental open-chest, heart-paced dogs before and after a single 1 mg/kg dose of E. coli endotoxin under pentobarbital anesthesia. Positive maximal dp/dt, time to peak ventricular pressure (PVP time), cardiac output, stroke work, tension-time index (TTI), coronary flow, and cardiac oxygen consumption were derived from left ventricular pressure, aortic flow, left atrial pressure, coronary sinus flow and A-V oxygen difference. During a control period and for 2 h post-endotoxin, while mean arterial pressure (afterload) and heart rate were held constant, +dp/dt max, PVP time, cardiac output, and cardiac work were related to left ventricular end diastolic pressure to obtain ventricular function curves. Positive maximal dp/dt was found depressed early (60 min) during the 2 h period of endotoxicosis studied (P less than .05). PVP time values increased after endotoxin administration but not significantly. Coronary sinus flow was found to be significantly elevated at 2 h post-endotoxin. The findings indicate the presence of early (60 min) and sustained depression of ventricular performance at elevated coronary blood flows during endotoxicosis.