The haemodynamic values before and immediately after direct myocardial revascularization were compared in 14 patients with ischaemic heart disease. Within the first hours after surgery cardiac output decreased to 50% of the preoperative value owing to a decrease in stroke volume, wedge pressure was increased, and systemic pressure was maintained at preoperative values by a rise in peripheral resistance. After the initial decrease cardiac output again increased to preoperative values (after 7 h) and above these values (19 h after surgery). Systemic blood pressure decreased owing to rapidly decreasing peripheral resistance. Knowledge of the pattern of haemodynamics in the early postoperative period facilitates the diagnosis of untoward circulatory episodes and permits to distinguish the effect of therapy from the haemodynamic changes normally occurring during this period.