To clarify the mechanisms of a prompt decrease in cardiac output following burns, we studied left ventricular (LV) contractility and distensibility after full-thickness 50% total body surface area burns in anesthetized dogs during a 6-h postburn period. Contractility was assessed from the end-systolic pressure-volume relationship (ESPVR) and the stroke work-end-diastolic volume relationship (the preload recruitable stroke work relationship; PRSW). LV chamber distensibility was also assessed from the end-diastolic pressure-volume curve. The PRSW slopes in the burn group showed a significant decrease compared with those in the control group (P less than 0.05), indicating burn-impaired contractility. The ESPVR shifted significantly rightward without changes in its slope after burns (P less than 0.02). This also suggested that contractility was depressed by burns. On the other hand, there was no significant change in the indexes of chamber distensibility between the two groups. We therefore concluded that burns decreased contractility as well as preload but did not change end-diastolic distensibility during this early postburn period.