We compared in vitro antibacterial activity of DWC-751, a new parenteral cephalosporin antibiotic, with those of cefpirome (CPR), cefotaxime (CTX) and ceftazidime (CAZ). DWC-751 showed a broad antimicrobial spectrum against Gram-positive and negative bacteria The antibacterial activity of DWC-751 against Stapylococcus aureus was equal to that of CPR and superior to those of CTX and CAZ. The activity of it against Escherichia coli was more potent than those of CPR, CTX and CAZ. Against Pseudomonas aeruginosa, DWC-751 was slightly inferior to that of CAZ and superior to those of CPR and CTX. The antibacterial activity of DWC-751 was superior to those of CPR, CTX and CAZ against clinical isolates and ofloxacin resistant strains. DWC-751 showed bactericidal action against Escherichia coli at concentrations close to the MIC and induced the formation of filament and burge and lysis of Escherichia coli in a microscopic examination.