The value of chemical characters in the taxonomy of mushrooms of the genus manita was investigated. Many specimens of different species were examined to determine the population variation in content of: a) tryptamines (bufotenine, 5-HT, and 5-HTP), b) cyclopeptides (amatoxins and phallotoxins), and c) isoxazoles (ibotenic acid and muscimol). Various species of Amanita were screened for the occurrence and for the amounts of toxins to evaluate their potential for toxicity. The three classes of compounds seem to be restricted to specific sections of the genus, supporting the sectional divisions made on morphologic grounds. No evidence of hybridization was found in sect. Amanita.