AIM To determine whether ONO 1078 {pranlukast, 4 oxo 8 [p (4 phenylbutyloxy) benzoyl amino] 2 (tetrazol 5 yl) 4H 1 benzopyran hemihydrate}, a potent leukotriene antagonist, has protective effect on focal cerebral ischemia in mice. METHODS Focal cerebral ischemia was induced by permanent middle cerebral artery (MCA) occlusion in mice. ONO 1078 (0 01, 0 05, 0 10 mg·kg -1 ), dexamethasone (0 5 mg·kg -1 ), nimodipine (0 2 mg·kg -1 ) or saline (control) were injected ip once daily for 3 days, and 30 min before MCA occlusion. Twenty four hours after cerebral ischemia, the neurological scores were evaluated, infarct volumes and areas of the right and left cerebral hemispheres were measured by computer imaging analysis. RESULTS ONO 1078, dexamethasone and nimodipine reduced the neurological scores. ONO 1078 and dexamethasone reduced the ratio of right/left hemisphere area, indicating inhibition of brain edema, while nimodipine showed no effect. ONO 1078 dose dependently reduced infarct size, and dexamethasone and nimodipine showed the same effect. CONCLUSION ONO 1078 showed protective effect on focal cerebral ischemia. This may represent a novel approach to the treatment of acute cerebral ischemia.