The rapid inhalation induction of anesthesia (RII) by mask inhalation of halothane, enflurane, isoflurane and sevoflurane at an equianesthetic concentration (2.5 MAC) was evaluated in 24 beagle dogs. The differences in movements, induction and intubation time between anesthetics were mainly associated with the differences in each blood/gas solubility. The most rapid and smoothest induction was observed by sevoflurane inhalation (209.0 +/- 44.2 sec), followed by isoflurane inhalation (285.8 +/- 34.1 sec). Halothane inhalation took the longest induction time (790.3 +/- 75.7 sec). Movements during RII were minimal in sevoflurane group comparing to the other groups. Heart rate, cardiac output and rate pressure product significantly increased after the beginning of inhalation in all the dogs except for those of halothane group. These changes exceeded the physiological level just after the beginning of inhalation, however, rapidly reversed to the maintenance level (1.5 MAC) approximately 10 min after intubation. Consequently, sevoflurane seemed to be the best inhalational anesthetic for RII in dogs without significant problems in respiratory and/or cardiac functions. Isoflurane also induced rapid induction with some degree of the movements.