Thioformamide derivatives of the formula: ##STR1## wherein R represents hydrogen or alkyl of 1 through 4 carbon atoms, and (i) Het represents a heterocyclic radical selected from pyrid-3-yl, pyrid-4-yl, pyridazinyl, pyrazinyl, pyrimidinyl, quinolyl, imidazolyl, naphthyridinyl, quinoxalinyl and quinazolinyl, X represents sulphur or oxygen and Y represents sulphur or oxygen, a valency bond or methylene, or (ii) Het represents pyrid-2-yl, X represents sulphur or oxygen and Y represents sulphur or oxygen or methylene, or (iii) Het represents pyrid-2-yl, X represents oxygen and Y represents a valency bond, are new compounds possessing useful pharmacological properties. They are particularly useful in the treatment of gastrointestinal ulcers and in the treatment of hypertension, depending on the definition of the symbol Het.