The authors evaluated the sigmoidal administration of methohexital, the effect of methohexital concentration (1% versus 2%), the effect of dosage (25 mg/kg versus 15 mg/kg) on sleep-success rate, administration - sleep time, recovery time and the effect of aspirating the residual methohexital on recovery time. The study demonstrated that both 1% solution and 25 mg/kg of sigmoidal methohexital were independently associated with significantly higher sleep success rate and faster onset of sleep compared with 2% and 15 mg/kg of sigmoidal methohexital solution respectively. The recovery time was significantly affected by the dose of methohexital and was not significantly affected by the concentration of methohexital solution. Aspiration of the residual methohexital did not significantly affect the recovery time.