The present invention relates to crystalline forms of [3-(4,5-dihydro-3-isoxazolyl)-2-methyl-4-(methylsulfonyl)phenyl]-(5-hydroxy-1-methyl-1H-pyrazol-4-yl)methanone,which is also known by the common name topramezone. Topramezone is aherbicidalactive substance of the formula I and also the tautomer of the formula I':(see formula I) (see formula I')The invention also relates to a method for the production of these crystallineforms, andto formulations which contain one of these crystalline forms of topramezoneforprotecting plants.
