Ibotenic acid (α-amino-3-hydroxy-5-isoxazole acetic acid) was separated from spores and caps from Amanita muscaria by reversed phase high performance liquid chromatography and identified by flow injection analysis with mass spectrometric detection. The keto and enol tautomers of ibotenic acid were separated and their ratio of 96:4 in favour of the enol form was determined. On average the ibotenic acid content was 0.0054±0.0010% of the spores and 0.017±0.010% in fresh caps. Muscimol, the decarboxylated product from ibotenic acid, was neither detected in spores nor in caps. 50 nanomol of ibotenic acid, muscimol or extracts from spores or caps did not inhibit the growth of Bacillus subtilis.