Although moxalactam is not, technically speaking, a cephalosporin it is chemically and microbiologically so closely related to those compounds that it can be viewed as a member of the cephalosporin family. Moxalactam has a spectrum of activity that includes both gram positive and gram negative bacteria. Its gram positive activity is less than earlier cephalosporins, but its activity against the Enterobacteriaceae is similar to that of the aminoglycoside family of antibiotics in most comparative studies. Although moxalactam is considerably less active against gram positive bacteria than cefotaxime, another third generation cephalosporin, its higher and more prolonged serum levels probably offset this disadvantage. Compared to cefoperazone, the stability of moxalactam to many types of beta lactamases produced by gram negative bacteria may be advantageous in the therapy of infections caused by hospital-acquired pathogens. Clinical studies suggest that moxalactam can be used for empiric therapy of suspected gram negative infections when Pseudomonas and other non-fermentative bacteria, such as Acinetobacter, are not suspected. Impressive improvements in the survival of patients with gram negative enteric bacillary meningitis have been reported. Although moxalactam, cefotaxime, and cefoperazone have activity against Pseudomonas aeruginosa, none of these antibiotics should be used alone as therapy for suspected or proven severe systemic infections caused by this pathogen. Cost is a major problem with all of the new cephalosporin-like antibiotics. While this high cost may be partially balanced by the use of a single agent compared to an antibiotic combination for therapy in some situations, these antibiotics are not cost effective for prophylactic use. Superinfection with fungi, such as Candida, and Streptococcus faecalis have occurred, and toxicities, such as bleeding due to vitamin K deficiency and disulfuram-like reactions, have also been reported. Reports of resistance to moxalactam and the other third generation cephalosporins are of major concern and indicate the need to closely monitor antibiotic susceptibility patterns of hospital acquired organisms if these antibiotics are to be used for empiric therapy of suspected gram negative non-pseudomonas sepsis.