Propofol (2,6-diisopropylphenol) 2.5 mg.kg-1 IV was compared with thiopentone 5 mg.kg-1 IV as an induction agent in anaesthesia for elective cardioversion. Thirty-five patients (ASA physical status II-III) with atrial fibrillation were included. Thirty patients were randomized to receive propofol or thiopentone. Five patients were treated twice during the study period and anaesthetized with both agents (the first treatment according to the random order and the second with the agent not used on the first occasion). The induction characteristics and the haemodynamic response for propofol and thiopentone were similar. The success rate of cardioversion did not differ between the groups. Recovery times were shorter after propofol than after thiopentone with respect to ocular muscle balance, central integration and subjective sedation of patients. The incidence of side-effects did not differ between the groups. None of the patients reported any awareness during the procedure. All five patients treated twice (with both agents) assessed the anaesthetic procedure with propofol as being more pleasant than that with thiopentone.