The invention concerns the treatment of ulcers and hypersecretion in a mammal using compounds of the formula I Ar--A--S--Y I where Ar is phenyl, which may be substituted or cycloalkyl of 5 to 7 carbon atoms, A is saturated or unsaturated lower alkylene which may be substituted by lower alkyl, oxo or hydroxy, S is sulphur and Y is an optionally substituted pyridine, pyridinium, tetrahydropyridine or tetrahydropyridinium radical. Certain novel compounds and pharmaceutical compositions are also disclosed.