To examine the working memory performance, gerbils were tested in the delayed nonmatching to position task using a T-maze, and the effects of cerebral ischemia on the performance were examined. There were no significant differences between gerbils and rats in the alternation performance without delay and with the interrun intervals ranging from 10 to 810 sec. These data suggest that this task is useful for assessing working memory in gerbils as well as in rats. Scopolamine (0.1 and 0.2 mg/kg) impaired the working memory performance in both species. Bilateral occlusion of the common carotid arteries for 5 min severely impaired the choice accuracy in the gerbils 1 to 3 days after the operation. This memory impairment was observed even at the shortest interval. One month after the operation, partial behavioral recovery was observed in the ischemic gerbils, in spite of a marked loss of the pyramidal cells in the hippocampus CA1 sector. These data indicate that the working memory performance is highly vulnerable to the cerebral ischemia and that the ischemic operation transiently but severely impairs the acquisition process of the working memory in gerbils.