Abstract: The present invention provides a compound of the formula (I) ##STR1## wherein: R.sup.1 is 1-hydroxyethyl, 1-fluoroethyl or hydroxymethyl;R.sup.2 is hydrogen or C.sub.1-4 alkyl;Z is carboxy, sufonic acid, tetrazol-5-yl or C .sub.1-4 alkylsulfonylcarbamoyl (--CONHSO.sub.2 C.sub.1-4 alkyl);A is a phenyl or thienyl ring;and A is optionally further substituted by one or two substituents or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof. Processes for their preparation, intermediates in their preparation, their use as therapeutic agents and pharmaceutical compositions containing them.

Abstract: Cephalosporin antibiotics having a 3-position substituent of the formula: ##STR1## are described, wherein R.sup.1 is hydrogen or certain optionally substituted alkyl groups; X is a benzene ring or certain 5 or 6-membered heterocyclic ring and is fused to ring Y which is a nitrogen containing heteroaryl group; R.sup.2 and R.sup.3 are independently hydroxy or an in vivo hydrolysable ester thereof, and ring system X-Y is optionally substituted. Processes for their preparation and use are described.