We studied 411 children aged 3-10 years who were referred for dental treatment. They were randomly allocated to have inhalation conscious sedation with either sevoflurane/nitrous oxide mixture or nitrous oxide alone. Dental treatment was satisfactorily completed in 215/241 children who were given sevoflurane/nitrous oxide mixture (89%) compared with 89/170 who were given nitrous oxide alone (52%) (Chi square 70.3, p < 0.0001). All children remained conscious and responsive to verbal contact throughout the treatment and in the recovery room. No adverse side-effects were recorded in either group and there were no significant differences in oxygen saturation, heart rate, recovery profile, or time to discharge home between the groups. The study concluded that, for every 100 children treated with sevoflurane/nitrous oxide mixture, 37 children would be saved a general anaesthetic if given combined sevoflurane and nitrous oxide mixture rather than nitrous oxide alone. The use of sevoflurane in low concentrations 0.1-0.3% to supplement nitrous oxide and oxygen for inhalation conscious sedation is safe, practical, and significantly more effective than nitrous oxide alone in children having dental treatment.