A process for preparing the crystalline modification II of the anhydrate of boscalid comprising: heating a solid boscalid starting material to an elevated temperature, the elevated temperature being below the melting point of the solid boscalid starting material and sufficient to preferentially form the crystalline modification II of the anhydrate of boscalid. Preferably the boscalid starting material comprises the crystalline modification I of the anhydrate of boscalid. Also preferably the elevated temperature is between 45-100°C and heating of the boscalid starting material is at a rate of from 5 to 35°C/hour. The boscalid material may then be cooled from the elevated temperature under an inert atmosphere at a a rate of from 5 to 35°C/hour. Also claimed is a fungicidal composition comprising the crystalline modification II of the anhydrate of boscalid.
