The role of the anterior thalamus (AT) in spatial working memory is well established. The involvement of the AT nuclei in tasks of object recognition is less clear. Two tasks of working memory were used to assess the extent to which NMDA lesions to the AT of rats, or a constituent structure, the anteroventral nucleus (AV), impair spatial and nonspatial working memory. An additional group consisted of lesion to the laterodorsal (LD) thalamic nucleus. Impairment was found for the AT group on an operant, spatial working memory task, the delayed non-matching to position task (DNMP). Neither the AV nor LD groups revealed any deficits on this task. Variations of intertrial interval (ITI) revealed that ITI of ten seconds produces proactive interference on the DNMP as compared with ITI of thirty seconds. All groups performed significantly better in the latter condition. The object recognition task revealed that all rats were able to recognize a familiar object after delays ofup to thirty minutes, but no group differences were found. No evidence was found for the inclusion of the LD as part of the AT complex.