/? (3-amino-l,2,4-triazolyl-l-) a-alanine is the major metabolic product of 3-amino-1,2,4-triazole in bean and tomato plants. Its preparation from aminotriazole-treated bean plants is described. The metabolite is translocated through both phloem and xylem systems; it is quite stable in the plant. The formation of ATX results in detoxication and is probably the cause of recovery of plants treated with sublethal doses. The relation of the substance to various metabolites of aminotriazole described earlier is discussed.