Disulfiram (Antabuse)-like reactions occurring in patients undergoing antibacterial therapy with certain cephalosporin antibiotics, and after ingestion of ethanol, are well documented. A murine model is described which may prove useful in the detection of compounds likely to produce this effect. Eight cephem compounds (moxalactam, cefamandole, cefmetazole, cefonicid, cefmenoxime, cefoperazone, cefotiam, ceforanide) each carrying an N-methyltetrazolethiol substituent in the 3-position of the dihydrothiazine ring of the parent antibiotic were capable of inducing a disulfiram-like reaction in the test animals. Evidence is presented which strongly suggests a direct relationship between N-methyltetrazolethiol and related heterocyclic thiols and the ability to induce this reaction.