In order to study cell proliferation after ischemic infarction, a model of bilateral common carotid artery occlusion in the gerbil was developed. A comparison of survival rates after 15, 30, 45 and 60 min of occlusion revealed that 45 min was the maximum duration of ischemia after which most (72%) of the gerbils were alive at 1 week. The administration of pentobarbital (single dose, 30 mg/kg) postoperatively to badly seizing animals increased survival to 100%. Large, well-demarcated infarcts were present in posterior thalamus or midbrain in 62% of gerbils subjected to 45 min bilateral occlusion. In 60% of these animals the infarcts were unilateral; in 40% they were bilateral. To quantitate cell proliferation in the infarcts from 12 h to 25 days after ischemia, gerbils were injected with [3H]thymidine 4 h prior to sacrifice, and autoradiographs were prepared from sectioned brains. Proliferation took place from 2 to 7 days after occlusion, with a maximum of 24% labeled cells at 6 days.