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Introduction: Lesion of the fimbria-fornix causes dysfunction of learning processes and has been used in animal models for the study of Alzheimer's disease., Material and Methods: With the objective of comparing the efficacy of two methods of producing a lesion of the fimbria-fornix, 40 young male Sprague-Dawley rats were distributed in four experimental groups: control (6), falsely lesioned (8), lesion due to aspiration (12) and lesion due to transection (14)., Results: The results showed that whilst with both techniques, in rats, serious cognitive defects were produced, as expressed by the high latencies of escape and small number of crossings of Morris's aquatic labyrinth, the aspiration lesion led to greater mortality than the transection lesion did. Similarly, the aspiration technique in rats induced hyperactivity, aggressiveness and tigmotaxia, while in the rats with lesions due to transection tigmotaxia ceased after their first attempts and hyperactivity on the second day of training., Conclusion: These results would suggest that a bilateral lesion due to transection of the fimbria-fornix is an effective alternative to an aspiration lesion to interrupt this pathway.