Objective: The study was undertaken to investigate the influence of TIVA with propofol, midazolam and fentanyl (comaintenance, COM-group) or TIVA with propofol and fentanyl (control-group) on sympathoadrenergic and hemodynamic reactions, stress response, EEG and recovery., Methods: After ethical approval, 2 x 20 patients of ASA-risk I - III over 55 years of age undergoing visceral surgery were investigated in a prospective randomized design. For induction of anesthesia, patients of the COM-group received 0,05 mg/kg BW midazolam und 1,0 mg/kg BW propofol, and anesthesia was maintained with 0,05 mg/kg BW/h midazolam (until 15 - 30 min before the end of the operation) together with propofol in decreasing doses of 10 - 5 - 2 mg/kg BW/h. In the control-group, 2,0 mg/kg BW propofol were used for induction followed by decreasing doses of 10 - 5 - 2 mg/kg BW/h as well. Premedication (0,1 mg/kg BW midazolam orally) and weight-dependent doses of fentanyl (2,5 microgram/kg BW for induction, 1,25 microgram/kg BW 2 min before skin incision, further repetition doses of 1,25 - 2,5 microgram/kg/BW as required) and vecuronium were equal in both groups. Beyond consumption of anesthetics and recovery, sympathoadrenergic, other endocrine and hemodynamic reactions and SEF 90 were investigated at 7 time points before induction and postoperative recovery. alpha 70 years) and duration of anesthesia and operation were comparable in both groups. Consumption of midazolam was higher in the COM-Group (14,8 vs. 7,5 mg; p = 0,004), whereas doses of fentanyl and vecuronium were comparable in both collectives. Recovery was significantly (p = 0,004) delayed in the COM-group: observing of simple orders 12,6 vs. 5,8 min, orientation with respect to person 19,8 vs. 9,9 min, local orientation 23,1 vs. 11,3 min. Mean arterial pressure in the COM-group was throughout lower than in the control-group, whereas heart rate was higher during the course of operation. Endocrine stress parameters (adrenaline, noradrenaline, antidiuretic hormone, adrenocorticotropic hormone, cortisol) and spectral edge frequency (SEF 90; Dräger-pEEG) were comparable in group level and time course between both groups. Plasma-concentrations of midazolam were significantly higher in the COM-group., Conclusion: In elderly patients undergoing visceral surgery in TIVA and when compared with propofol alone, no benefit of coinduction and comaintenance with midazolam and propofol could be demonstrated with respect to hemodynamic reactions and sympathoadrenergic and other endocrine stress response as well. Recovery was significantly delayed after administration of midazolam.