A rapid method combining gyrA PCR-restriction fragment length polymorphism analysis, parC PCR and adonitol fermentation was developed to identify Klebsiella pneumoniae phylogenetic groups KpI, KpII and KpIII. Analysis of 420 clinical isolates from 26 hospitals showed that the three groups were widespread geographically. KpI comprised 80.3% of 305 isolates from blood and 82.2-97.2% of isolates from other clinical sources. KpIII was never found among isolates from urinary tract infections. KpI isolates from blood were generally less susceptible than KpIII isolates to the ten antimicrobial agents tested, with KpII being intermediate. The frequencies of ceftazidime resistance were 21.6% and 8.6% in KpI and KpIII isolates, respectively (p 0.01).