Equine leukoencephalomalacia @LEV, swine pulmonary oedema and human oesophageal cancer have been associated with fumonisine B1 (FB1) ingestion. For the first time in this study it is reported that FBI was identified as being associated with an outbreak of ELEM at Oaxaca, Mexico. Symptoms of ELEM and Equine Venezuelan Encephalitis (EVE) are s d a r and a different diagnosis is obhgatory. In the geographical area (Oaxaca, Mexico) where donkeys died showing a neurological syndrome, 14 corn samples were collected. With the use of TLC Thin layer chromatography) and HPLC (High performance liquid chromatography) all collected samples resulted positive to FB1. In the area of study, this syndrome was reported to be the cause of death of 100 donkeys, after 3 postmortem examinations in which macroscopic and yicroscopic cerebral white matter liquefactive necrosis were observed, when FBI concentration was determined in the samples collected, using HPLC and TLC. It was concluded that HPLC is a highly sensitive method for the detection of FB1 through the formation of an OPA derivative. However, the reverse phase TLC plate nad the visualisation of the coloured reaction with the vanillin acidic solution is more objective. FBI concentration in the studied samples ranged from 0.67 to 13.3 ppm. It was concluded that FB1 was the causae of leukoencephalomalacia reported in donkeys in the state of Oaxaca, Mexico.