Effects of NB-818, a new Ca2+ entry blocker, on a transient cerebral ischemic model in Mongolian gerbils were examined. Following bilateral common carotid arteries occlusion of 20 min duration, all the control animals died within 24 hr after reperfusion. The administration of NB-818 at 0.1 mg/kg, i.p., 30 min after reperfusion significantly reduced the mortality rate to 65.0% (P less than 0.01); and 0.01 mg/kg, i.p., had a tendency to reduce the mortality rate. In the nimodipine-treated groups, a similar effects in the ischemic model. Furthermore, the administration of NB-818 at 0.1 mg/kg, i.p., 15 min before occlusion also had a tendency to reduce the mortality rate. On the incidences of seizures induced by transient cerebral ischemia, there were no significant differences between each of the drug-treated groups and the control group. In NB-818 and nimodipine-treated groups, the morbidity scores NB-818 and nimodipine in this severe cerebral ischemic model have advantages over those of nicardipine and flunarizine. Thus, these results suggest that NB-818 may be useful in the treatment of ischemic cerebral damage.