The in vitro activities of DA-074, a new cephalosporin against 34 various standard strains and its in vivo efficacies against 6 important strains were obtained. DA-074 showed two fold enhanced in vitro antibacterial activity against some Pseudomonas aeruginosa compared to Ceftazidime and more than 2 fold in vivo efficacy against Staphylococcus aureus Smith, Klebsiella pneumoniae 1 and Escherichia coli KC-14, compared to Cefpirome. DA-074 might be a good candidate for further evaluations.