The haemodynamic effects of intravenous tramadol (two different doses: 0.75 mg/kg b.w. or 1.5 mg/kg b.w.) during artificial ventilation with oxygen and nitrous oxide were investigated in 20 female patients before the start of operation. Haemodynamic changes were characterized by a moderate increase in blood pressure concerning systemic as well as pulmonary circulation. These effects were due to a rise in peripheral and pulmonary vascular resistance. Application of tramadol immediately after the end of operation (n = 20:10 patients following neuroleptanalgesia and 10 patients after anesthesia with halothane) led to a slight antagonizable decrease in respiratory frequency and respiratory amplitude as well as increase in paCO2. While during conventional pain-therapy no haemodynamic and respiratory side-effects of tramadol could be demonstrated, the typical qualities of opiates (postoperative ventilatory embarrassment) and unspecific adrenergic effects have to be taken into account after use of high doses for anaesthetic purposes.