The disulfiram-like reactions following the treatment of cephem antibiotics with methyltetrazolethiol moiety (latamoxef (LMOX) and cefoperazone (CPZ) was studied by using large (500 mg/kg) and small (50 mg/kg) doses of the drugs. Normal and fatty liver rats were injected intraperitoneally with the cephem antibiotics. After overnight fasting blood samples were obtained following an administration of 20% ethanol (2g/kg). Blood ethanol and acetaldehyde concentrations, and liver acetaldehyde dehydrogenase activity were determined. Blood ethanol concentration upon the small dose was similar to that obtained upon the large dose in both groups of normal and fatty liver rats. Blood acetaldehyde concentration upon the large dose was higher than that upon the small dose; 2-fold increase in normal rats and 2.6-4.7-fold increase in fatty liver rats were observed after administering LMOX, while 3.7-fold increase in normal rats and 5-5.7-fold increase in fatty liver rats upon administering CPZ. Additionally, liver acetaldehyde dehydrogenase activity (Enzyme 1) observed upon the large dose was lower than that observed upon the small dose; the degree of reduction was 33% in normal and 19% in fatty liver rats upon the administration of LMOX, while 37% in normal and 45% in fatty liver rats upon the administration of CPZ.