2-Substituted methylthio-3,5-dicyanopyridine derivatives (I), their salts and/or hydrates and solvates are new. 2-Substituted methylthio-3,5-dicyanopyridine derivatives of formula (I), their salts and/or hydrates and solvates are new. n = 2-4； R<；1>； = H or 1-4C alkyl； and R<；2>； = pyridyl or thiazolyl optionally substituted by 1-4C alkyl, halo, amino dimethylamino, acetylamino, guanidino, pyridylamino, thienyl, furyl, imidazolyl, (thio)morpholinyl, piperidinyl, piperazinyl (optionally N-substituted by 1-4C alkyl), pyrrolidinyl, oxazolyl, isoxazolyl, pyrimidinyl, pyrazinyl, thiazolyl (optionally substituted by 1-4C alkyl) or phenyl (optionally substituted by 1-3 of halo, 1-4C alkyl or alkoxy). An Independent claim is also included for a method for preparing (I) by reacting the corresponding 2-thiol with R<；2>；CH2X (III), where X = leaving group.
