Cardiovascular consequences of septic shock are well described in humans but have poorly been studied in horses. The endotoxins are known to induce a myocardial depression and a systemic hypotension responsible for a fall of both the cardiac output and the systemic vascular resistance in end-stage endotoxic shock. The aim of this study was to evaluate the impact of endotoxic shock on equine myocardial function. A total of 67 horses including 17 controls and fifty horses admitted in clinic with signs of endotoxic shock were submitted to a doppler echocardiographic exam. A shock score was attributed to each endotoxic horse on the basis of clinical evaluation, non invasive systolic blood pressure and blood tests. Score 1, 2, 3 and 4 included 11, 17, 12 and 10 horses, respectively. Echocardiographic and Doppler parameters were compared between the 5 groups using a multivariable ANOVA analysis. The ejection time (ET), the ET corrected for HR, the mean velocity of circumferential fibre shortening corrected for HR, the aortic velocity time integral and deceleration time, and the stroke volume were significantly lower, whereas the HR and the peak velocity of late diastolic filling of the mitral flow and its velocity time integral were significantly higher in endotoxic than in control horses. Even if the tachycardia, the fall in preload and a probable decrease in afterload influenced the observed changes, the results suggested that a myocardial depression with both an impaired systolic and diastolic left ventricular function could be a component of endotoxic shock in horses.