The purpose of this study was to investigate the usefulness of different molecular typing techniques in the surveillance and control of the spread of extended-spectrum-beta-lactamase-(ESBL) producing Klebsiella pneumoniae in the pediatric department of the "Agostino Gemelli" hospital of the Catholic University in Rome, over a period of nine months. The strains were characterized by ribotyping using HindIII as restriction enzyme and pulsed field gel electrophoresis (PFGE) using XbaI as endonuclease. Sixty six K. pneumoniae clinical strains were isolated during this period, the first 32 were isolated in the summer of 1998. Among these first isolates, ribotyping generated 26 different patterns whereas PFGE produced 16 patterns. The remaining 34 strains were isolated during January and April 1999 and all of them were ESBL producers. Ribotyping clustered the strains into 6 patterns whereas PFGE generated only 3 patterns. PCR revealed the presence in 10 isolates of both bla(TEM) and bla(SHV) genes and 24 strains carried only the bla(SHV) gene. In our experience ribotyping revealed a higher power of differentiation with respect to PFGE and was of great help in the surveillance of the infection.