The anesthetic and cardiopulmonary effects of a combination of continuous intravenous infusion using a mixture of 6 g L(-1) thiopental-75 g L(-1) guafinesine-3 mg L(-1) metedomidine (0.30 mL/kg/h) and Oxygen-Sevoflurane (OS) anesthesia (TGM-OS anesthesia) in horses were evaluated. The concentration of sevoflurane (Sevo) required maintaining surgical anesthesia was around 1.5% in TGM-OS and 3.3% in OS anesthesia. Mean Arterial Blood Pressure (MABP) was maintained at around 77 mm Hg under TGMOS anesthesia, while dobutamine (0.43 +/- 0.13 mu g kg(-1)) infusion was necessary to maintain MABP at 60 mmHg under OS anesthesia. No apparent complication was observed during and after anesthesia in all cases. Recovery from anesthesia tinder TGM-OS anesthesia was very calm and smooth. The times required for the horse to return both sternal and standing position in group under TGM-OS anesthesia tended to be shorter than group under OS anesthesia which statistical differences were p<0.05 and p<0.01, respectively. Thiopental Guafinesine-Metedomidine and Oxygen-Sevoflurane anesthesia (TGM-OS anesthesia) may be useful for prolonged equine anesthesia because of its minimal cardiopulmonary effects and good recovery from anesthesia.