Onset of rocuronium is rapid but relatively large doses are needed to achieve a suitable intubating condition. So we compared the single bolus injection with divided injection of rocuronium about tlie onset time, intubation time and intubating condition.

Thirty patients were divided into three groups of 10 each randomly. Patients in group I were given a single dose of 0.6mg/kg rocuronium. Those in group 2I or 3 received 0.06 mg/kg or 0.09 mg/kg as priming dose followed by 0.54 mg/kg and 0.81 mg/kg as intubating dose 3 min. later. The train of four responses of adductor pollicis muscle was recorded using Paragraph(Utah Medical Product Inc. Midvale Utah, U.S.A.) every 10 seconds. The trachea was intubated by one clinician who was blinded to the muscle relaxant administered when he thought the patients were suitable for intubation, and he recorded the intubating conditions. The endotracheal intubation time and twitch height at the moment was recorded by other clinician. The onset time was recorded when the post tetanic count is marked as '0'.

The onset time of group 1, 2, and 3 were 90.0±22.lsec, 109.0±35.0 sec and 85.0±35.0 sec. respectively. Endotracheal intubation times were 77.0±10.6sec, 60.0±10.0sec and 44.0±5.2sec respectively.

There was no differences about onset time between single and devided injection with same total dose or incremental dose of 0.9mg/kg. But the intubation time was faster in priming group with dose dependent manner, and the intubating conditions were excellent to good in all patients.