A method for producing highly crystalline and stable microparticles of an active substance with a very narrow size distribution. The microparticles being crystallized out of a suspension made of primary particles of the active substance, a solution of the active substance, a non-solvent for the active substance and inert formed pieces. The resulting microparticles hare are highly stable largely independent of the physiochemical properties of the active substance and can be especially suitable for fast release dosage forms of pharmaceuticals.