New semisynthetic cephalosporins characterized by having structures with a 1-carboxymethylthioethyltetrazolyl-5-thiomethyl group at position 3. Exemplary is the antibacterially effective 7-D-mandelamido-3-(1-carboxymethylthioethyltetrazolyl-5-thiomethyl)-3-ceph em-4-carboxylic acid disodium salt.