Abstract: Cephem compounds of the formula: ##STR1## wherein R.sup.1 is amino or a protected amino group,Z is N or CH,R.sup.2 is lower alkyl, mono(or di or tri)halo(lower)alkyl, lower alkenyl, lower alkynyl, phenyl, naphthyl, phenyl(lower)alkyl, carboxy(lower)alkyl or protected carboxy(lower)alkyl, andR is a group of the formula: ##STR2## in which R.sup.3 and R.sup.4 are each lower alkyl,A is lower alkylene, andR.sup.5 is hydroxy or a protected hydroxy group; or pharmaceutically acceptable salts thereof show antimicrobial activities and are useful in the treatment of microbial infections.