In a small open dose-finding study the i.v. dose of ICI 35 868 required to induce anaesthesia in healthy adults was 2 mg kg−1. Comparison of this dose with Aithesin 0.05 ml kg−1 for i.v. induction, both injected over 30 s suggests that they have similar effects on heart rate, arterial pressure and breathing. The mean times to loss of eyelash re:flex were 57±SD 10.1 s (ICI 35868) and 46±SD 3.9s (Aithesin). The new drug was associated with pain and discomfort on injection in seven of 10 patients, but with less involuntary movement than occurred with Althesin.