The effects of lesions of the horizontal nucleus of the diagonal band of Broca (HNDB) and the entorhinal cortex (ENTO) upon performance of a spatial location recognition task were assessed. Two hypotheses of entorhinal cortex function were considered in interpretation of the data. The first hypothesis assumes that the anatomical proximity and interconnections between the hippocampus and the entorhinal cortex are indicative of a functional similarity. The second hypothesis recognizes the interconnections of the hippocampus and the entorhinal cortex, but posits that the two structures have distinct functions. The hippocampus receives input primarily from the medial septum (MS), whereas the entorhinal cortex receives input from the HNDB and the MS. The study attempted to assess the function of the ENTO and the HNDB in a spatial location recognition task with the intent of comparing the findings to previous research of the hippocampus and MS. Performance of animals with HNDB lesions and the ENTO lesions was at chance levels for all serial positions. Results indicated that there are functional differences between the HNDB and other basal forebrain structures. Further, the performance deficit of the ENTO group does not differ from that observed following lesions of the hippocampus.