Abstract: The invention relates to novel halovinyl cephem derivatives of high antimicrobial activity of the formula: ##STR1## wherein R.sup.1 is a group of the formula:R.sup.4 --A--CONH--in which R.sup.4 is cyano(lower)alkenylthio or a group of the formula: ##STR2## in which R.sup.6 is hydrogen, amino or a protected amino group, andA is carbonyl, lower alkylene, hydroxy(lower)alkylene or a group of the formula: ##STR3## in which R.sup.5 is hydrogen, carboxy(lower)alkyl or protected carboxy(lower)alkyl;R.sup.2 is carboxy or a protected carboxy group; andX is halogen, and pharmaceutically acceptable salts thereof.