The present invention relates to two crystalline forms of2-[2-chloro-4-methylsulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)benzoyl]cyclohexan-1,3-dione offormula l, which is also known under the common name tembotrione. Theinventionalso relates to a process for the production of these crystalline forms andformulations for plant protection which contain one of these crystalline formsoftembotrione.(see formula I)