The predictive value of in vitro time-kill curve was tested on an Enterobacter cloacae endocarditis experimental model. The antibiotic studied was gentamicin. Despite a similar MIC, 2 Enterobacter cloacae strains exhibited very different time-kill curves in vitro. This difference was found being predictive of efficacy on the in vivo model, 24 hours after a single injection of gentamicin.