Cefonicid is a new second-generation cephalosporin with a broad antimicrobial spectrum of activity and a prolonged serum elimination half-life. It has good in vitro activity against methicillin-sensitive Staphylococcus aureus, nonenterococcal streptococci, Hemophilus influenzae, Neisseria gonorrhoeae, Neisseria meningitidis and many of the commonly isolated Enterobacteriaceae. Organisms usually resistant to cefonicid include species of Pseudomonas, Serratia, Acinetobacter and Providencia, and Bacteroides fragilis. The drug is 98% protein bound in human serum, which probably contributes to its significant reduction of antimicrobial activity measured in serum. Limited clinical trials have demonstrated it to be effective for surgical prophylaxis and for treating infections of the urinary tract, lower respiratory tract and bone. Failures have been reported in treatment of soft tissue infections and endocarditis caused by S. aureus.