Sixty-four women undergoing non-abdominal operations were anaesthetized with ketamine administered as continuous intravenous drip combined with diazepam. A double-blind, controlled study was done to assess the dosage, the cardiovascular stimulation, and whether psychotomimetic side effects could be reduced. At induction ketamine was given in a dose of 2 mg/kg in combination with diazepam/placebo 10 mg i.v. The infusion was maintained at 2-6 mg/min. The dose of ketamine during the anaesthesia was significantly reduced by diazepam, from 4.51 mg/min to 3.55 mg/min (p less than 0.001). The sympathomimetic effect of ketamine was significantly reduced by diazepam, as the increase in pulse rate as well as in blood pressure was diminished (p less than 0.05). The frequency of hallucinations dropped from 30.0% to 2.9% with diazepam, while the total frequency of psychotomimetic side effects fell from 36.6% to 11.8% (p less than 0.05). As this frequency of the psychotomimetic side effects still seems to be high with this method, it cannot be recommended to use a continuous drip of ketamine for routine operations on adults. On the other hand, ketamine infusion was found to produce favourable haemodynamic conditions, and this technique seems to be useful in poor-risk and hypovolaemic patients.