We have studied cefuroxime, a new beta-lactamase resistant cephalosporin, and cefoxitin, the first cephamycin antibiotic, which is also resistant to many beta-lactamases. Both of these antibiotics have been shown to be microbiologically superior to the "first generation" cephalosporins, cefuroxime having notable activity against Haemophilus influenzae, and cefoxitin against Bacteroides fragilis. Neither antibiotic is absorbed from the gut but, following parenteral administration, serum, urine and bile concentrations are high. Clinical trials have been conducted on both cefoxitin and cefuroxime. The results of these have been satisfactory and untoward side-effects minimal. We suggest that cefoxitin will be particularly valuable in the management of abdominal sepsis and cefuroxime in infections caused by H. influenzae.