In 104 premedicated patients undergoing general surgery, anaesthesia was induced either with etomidate 0.3 mg kg-1 preceded by fentanyl 1.25 or 2.5 microgram kg-1 i.v.or diazepam 0.0625 or 0.125 mg kg-1 i.v., or with thiopentone preceded by fentanyl 1.25 microgram kg-1 i.v. Despite the use of fentanyl or diazepam, the frequency of pain on injection in patients receiving etomidate was between 32% and 53%, being rated as severe in 5-20% of patients. No pain was experienced by patients receiving thiopentone. The frequency of involuntary movement was 15-35% with etomidate and 15% with thiopentone. The frequency of both pain and involuntary muscle movements was least when fentanyl 2.5 microgram kg-1 preceded the administration of etomidate. There was no significant relationship between the pain and muscle movement; three of 10 patients given etomidate into a central vein had such movements.