It was studied the amino acids pattern in serum and cerebrospinal fluid of 12 and 8 patients, respectively, suffering from optic epidemic neuropathy diagnosed between 1995 and 1997 (endemic period). The cerebrospinal fluid of 16 patients diagnosed during the epidemic (1992) was also studied. The analysis of amino acids in serum and cerebrospinal fluid was made by high resolution liquid chromatography with fluorescent detection, previous derivation with orthofthallic aldehyde. As in the previous study, no important deficiencies of the essential amino acids were observed in the serum of the studied patients. Lower concentrations of threonine, aspartic acid and taurine were found in the serum of patients with epidemic optic neuropathy diagnosed in the endemic period. Taurine plays an important role in the structure and function of photoreceptors of the retina. It is synthesized in the necessary amounts in man, so it must be supplied in the diet. As it is only present in food of animal origin, it is considered that the deficiency of taurine may contribute to the development of optic epidemic neuritis in our patients. Samples of cerebrospinal fluid were analyzed during the epidemic and endemic periods and it was observed an increase of the glutamic and aspartic acid in the epidemic period and of glutamic acid during the endemic. The excess of excitotoxic amino acids in the cerebrospinal fluid supports the previous neurocognitive studies that suggested the affection of the central nervous system in these patients.