Background: The locations of cortex controlling motor, sensory, or language functions can change in adult humans under some circumstances, such as expanding tumours, trauma or continuous focal seizures. It is not clear what other circumstances might result in changes in cortical functional maps. Methods: The results of extraoperative cortical mappings of motor, sensory, and language functions were compared in two epilepsy patients who underwent cortical resections on two separate occasions and who did not have brain tumours. Results: It was found that the locations of motor functions could differ between the first and second procedures, but the locations of language functions were quite similar. The changes were not necessarily in or adjacent to epileptogenic regions or adjacent to resection boundaries. Conclusions: These findings support previous evidence indicating that cortical functional representations can change over time in humans, and suggest that these changes cannot be explained solely by lesion effects.