Three hours after dogs were given an intravenous injection of Escherichia coli endotoxin significant decreases in cardiac taurine levels were observed in the apex and epicardial regions of the right ventricle and in all regions sampled from the left ventricle. A decrease in taurine was seen in all regions of the heart (including the atria) by 90 min after endotoxin treatment but the results were not statistically significant. Echocardiography and left ventricular cannulation were used in a separate group to confirm that the dose of endotoxin used was adequate to produce depression of cardiac output and force of contraction.