The antibacterial activity of cefotetan, 8 other beta-lactam antibiotics and gentamicin, was tested in vitro on 288 recently isolated bacteria. The activity of cefotetan was generally higher than the 2.generation cephalosporin cefuroxime and lower than the 3.generation cephalosporins tested. In addition, cefotetan was shown to have some antibacterial activity against anaerobic bacteria. Cefotetan is a cephamycin and was found resistant to all 14 plasmid-mediated and 2 chromosomally-mediated beta-lactamases. With its beta-lactamase resistance and antibacterial activity, cefotetan seems to be a "second-generation-like" cephalosporin, almost with 3.generation cephalosporin antibacterial activity against Enterobacteriaceae.