Cephalosporins represented by the formula X-S-Y wherein X is a deacetoxycephalosporinyl group and Y is a 6-membered heterocyclic group containing 1-3 nitrogens at least one of which is substituted and at least one of which is adjacent to a carbonyl group, said heterocyclic group containing one or more ring substituents and being characterized by being non-aromatic and not enolizable to an aromatic form.