Thalamic contributions to memory were assessed in monkeys with lesions placed in the medial portions of either the anterior or posterior thalamus (AMT and PMT, respectively). Both lesions produced a moderate impairment in a test of object recognition memory. Furthermore, all three animals in the PMT group and two out of the three in the AMT group were moderately impaired on a test of object-reward associative memory. Comparison of these results with those of a previous study in which the AMT and PMT regions were removed jointly (Aggleton and Mishkin 1983) suggests that damage in either region can induce a memory loss but that combined damage to both is required to produce a full-blown amnesia.