Cephalosporin derivatives of the general formula

   in which R³ is a group of the formula

   R⁶⁰ and R⁶⁵ are hydrogen or lower alkyl, R¹⁵-R¹⁹ are each independently hydrogen, halogen or hydroxy, n is zero or 1, R⁴ and R⁵ are each hydrogen, halogen, lower alkyl, lower alkoxy or amino, R⁷ is hydrogen or lower alkyl and R⁸ is lower alkyl, halo- lower alkyl, C₃-C₇ cycloalkyl or mono-, di- or trihalophenyl, and Z is N or C-R⁹, where R⁹ is hydrogen, halogen, lower alkyl or lower alkoxy; and, when R⁴ is fluoro, R⁵ and R⁷ are hydrogen. R⁸ is cyclopropyl and Z is C-H, R³ can also be one of the groups

   in which R⁶¹ and R⁶⁶ are hydrogen or methyl, R¹⁵-R¹⁹ are as above and R⁹⁰ is hydrogen, hydroxy, carboxy, amino or [[4-(lower alkyl)-2,3-dioxo-1-piperazinyl]carbonyl]amino;
pharmaceutically acceptable acid or base addition salts thereof, hydrates of compounds of formula I and hydrates of such salts.
The products have antibacterial activity.