7-acetamidocephalosporins are disclosed herein which are substituted at position 3 of the cephalosporin nucleus with the group ##STR1## wherein R.sub.2 is selected from the group hydrogen, amino, C.sub.1 to C.sub.6 alkylamino and di-C.sub.1 to C.sub.6 alkylamino and R.sub.3, R.sub.4 and R.sub.5 are the same or different and are selected from the group hydrogen, hydroxy, C.sub.1 to C.sub.6 alkyl, C.sub.1 to C.sub.6 alkoxy, trifluoromethyl, phenyl, substituted phenyl, heterocyclic aryl, and R.sub.3 and R.sub.4 or R.sub.4 and R.sub.5 taken together are the moiety --CH.sub.2 (CH.sub.2).sub.2 CH.sub.2 --.