The invention relates to 4-substituted quinoline compounds of general formula: ##STR00001## which are active as antimicrobials, in which: X.sub.1, X.sub.2, X.sub.3, X.sub.4 and X.sub.5 is C--R'.sub.1, to C--R'.sub.5 respectively, or alternatively at most one represents N, Y represents CHR, CO, CROH, CRNH.sub.2, CRF or CF.sub.2, R being a hydrogen or alkyl, m is 1, 2 or 3 and n is 0, 1 or 2, Z is CH.sub.2 or Z is O, S, SO, SO.sub.2 and, in this case, n is equal to 2, R.sub.2 is --CO.sub.2R, --CH.sub.2CO.sub.2R, --CH.sub.2--CH.sub.2CO.sub.2R, --CH.sub.2OH or --CH.sub.2--CH.sub.2OH, wherein R is as defined above, R.sub.3 represents phenyl, heteroaryl or alk-R.sup.o.sub.3, where alk is alkyl and R.sup.o.sub.3 represents various groups, where appropriate containing oxygen, sulfur or amine, in their enantiomeric or diastereoisomeric forms or their mixtures, and/or where appropriate in the syn or anti form or their mixtures, and their salts.