A process for preparing clomazone is provided the process comprising reacting 4 4 dimethyl 3 isoxazolidinone with 2 chlorobenzyl chloride in an aqueous medium in the presence of a base in particular an alkali metal hydroxide. A method for preparing clomazone is also disclosed the method comprising (a) crystallizing clomazone from solution in an organic solvent and (b) isolating the resulting crystals. N benzene is a particularly suitable solvent. Further there is provided Form I crystalline 2 [(2 chlorophenyl)methyl] 4 4 dimethyl 3 isoxazolidinone (clomazone) wherein the polymorph Form I is characterized by at least one of the following properties : (i) an X ray powder diffraction pattern having characteristic peaks expressed in degrees 2(+/ 0.20� ) at one or more of the following positions : about 10.63 16.07 18.08 19.11 19.34 21.20 24.78 and 28.80 and (ii) an infrared (IR) spectrum having a characteristic peak : at about 2967 and 2870 cm.
