A monoclinic crystalline form of asenapine maleate is described, which is characterized in that it is not micronised and has a particle size distribution characterized by a d90 of 40 μm or less. A process for the preparation of a monoclinic crystalline form of asenapine maleate is also described, the process comprising the following steps: a) providing a mixture of monoclinic asenapine maleate and an organic solvent which, under the conditions of the process, acts as an antisolvent; b) stirring the mixture at a temperature between 15 and 60° C.; and c) collecting the crystals, wherein the organic solvent is selected from alcohols, ketones, ethers, esters, hydrocarbons or mixtures thereof.