A re-evaluation is made of those aspects which led to the etiologic diagnosis in 353 patients who suffered from non-traumatic, non-tumoral myelopathies, and whose cases were studied along a period of 20 years. The cases were distributed as follows: syringomyelia, 5 cases; vascular myelopathy, 15 cases; privation caused myelopathies, 67 cases; infectious or infestation caused myelopathies, 82 cases; post-vaccination, post-infection or post-intoxication, 31 cases; multiple sclerosis and optic neuromyelitis, 20 cases; primary myeolopathy, 133 cases. With basis on the diagnosis, those aspects which may contribute to the existing knowledge about physiopathologic mechanisms related to the onset of spinal cord involvement, as related to immunobiologic alterations, are analysed. The role of necrosis, demyelinization and inflammation, and their respective interrelashionships are considered in this light.