Cephalosporins represented by the formulaX--S--Ywherein 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 non enolizable to an aromatic form.