The in-vitro activity of SR 44337 was compared with that of other broad-spectrum parenteral cephalosporins, plus imipenem and co-amoxiclav. SR 44337 showed good activity against the Enterobacteriaceae, with MIC90s of less than 0.5 mg/L against all species tested, with the exception of Citrobacter spp. (MIC90 2 mg/L) and Serratia spp. (MIC90 4 mg/L). Of the agents tested, only ceftriaxone showed consistently greater activity against this family of organisms. SR 44337 had higher activity than ceftriaxone against Acinetobacter spp. and Pseudomonas aeruginosa, and was the most active agent tested against Neisseria meningitidis (MIC90 0.004 mg/L). All strains of N. gonorrhoeae, Haemophilus influenzae and the streptococci (excluding the enterococci) were susceptible to less than or equal to 0.25 mg/L of SR 44337, which was also the most active cephalosporin tested against Staphylococcus aureus. SR 44337 was stable to hydrolysis by the TEM-1, SHV-1 and P99 beta-lactamases, and was more stable than ceftriaxone to the K-1 beta-lactamase.