This application concerns quinoline derivatives of formula I ##STR1## and pharmaceutically acceptable acid addition salts thereof, wherein X represents CSNHR.sup.1, where R.sup.1 represents hydrogen or lower alkyl, R.sup.2 and R.sup.3 are the same or different and represent hydrogen or lower alkyl, R.sup.4 represents hydrogen or single or multiple substitution by lower alkyl and n is 1, 2 or 3. These compounds are anti-ulcer agents.