Effects of medetomidine (40 micrograms/kg)-midazolam (0.2 mg/kg) on plasma glucose and insulin concentrations were evaluated in laboratory pigs. Intramuscular injection of medetomidine-midazolam induced a gradual hyperglycemic response associated with hypoinsulinemia which was much smaller than that by 80 micrograms/kg of medetomidine alone and was almost within a physiological fluctuation. These mild responses induced by medetomidine-midazolam were antagonized by use of an alpha 2-adrenoreceptor antagonist atipamezole (160 micrograms/kg), therefore those changes were thought to be mainly attributed to the effect of medetomidine on alpha 2-adrenoreceptors. A combination of medetomidine at a low dose and midazolam reduces undesirable effects, while providing more profound sedation than medetomidine alone in laboratory pigs.