Novel cephalosporins of the general formula (I); STR1 in which R is alkyl, L-2-amino-2-carboxy-ethyl, phenyl, pyridyl, pyridyl-N-oxide, pyrimidin-2-yl, substituted pyridazin-3-yl, 5,6-dioxo-1,4,5,6-tetrahydro-1,2,4-triazin-3-yl substituted in the 4-position, 1,3,4-triazol-5-yl or 2-alkoxycarbonyl-1,3,4-triazol-5-yl substituted in the 1-position, 1,4-dialkyl-5,6-dioxo-1,4,5,6-tetrahydro-1,2,4-triazin-3-yl, 1-alkyl-5,6-dioxo-1,4,5,6-tetrahydro-1,2,4-triazin-3-yl, 2-alkyl-5,6-dioxo-1,2,5,6-tetrahydro-1,2,4-triazin-3-yl, triazol-5-yl, 1,3,4-thiadiazol-5-yl which is substituted or unsubstituted, 1,2,4-thiadiazol-5-yl which is substituted, 1,3,4-oxadiazol-5-yl which is substituted or unsubstituted, oxazol-2-yl which is substituted or unsubstituted or tetrazol-5-yl which is substituted or unsubstituted in the 1-position, R' is a hydrogen atom or a radical of the general formula (II); STR2 and Ro is hydrogen, alkyl, vinyl or cyanomethyl, as well as their salts, are useful as anti-bacterial agents.