The present invention concerns a method for coating granules comprising mesalazine, with a coating mixture comprising two polymers, polymer I and polymer II; said polymer I being selected to allow formation of a closing membrane around said granules in the absence of said polymer II, and said polymer II being selected to act as a water-soluble pore former in said coating mixture; wherein a) the amount of polymer I is adjusted to provide a closing membrane in the absence of polymer II, and b) the amount of polymer II in said coating mixture is adjusted to obtain coated granules which exhibit controlled release of mesalazine. The invention further concerns a product obtainable by the coating method.