ABSTRACT:We describe a method for making selective lesions of the hippocampus in macaque monkeys, using a magnetic resonance imaging (MRI)-guided stereotaxic approach in which the excitotoxin N-methyl-Daspartic acid (NMDA) is injected at intervals along a single needle track that extends longitudinally through the rostrocaudal extent of the hippocampus. Procedures were conducted on six rhesus monkeys (Macaca mulatta) and were assessed with either in vivo MRI (n ‫؍‬ 3) or postmortem microscopic examination of the tissue after standard histological processing of the brains (n ‫؍‬ 3). Based on our extensive experience with the standard stereotaxic procedure in which ibotenic acid (IBO) is injected via the dorsal approach, we report that the new method provides a viable and potentially advantageous alternative to the standard procedure.