During the first quarter of 1996, a major outbreak of clinical infection caused by multiresistant Klebsiella pneumoniae (MRKP) occurred in the neonatal ward of the 'Maternité Wassila Bourguiba' in Tunis, Tunisia. In total, 32 isolates of MRKP, comprising 23 clinical isolates and nine surveillance isolates, were recovered during this period and analysed for epidemiological relatedness. The isolates were compared with 17 other isolates of MRKP that were recovered during 1995. Macrorestriction profiles of total genomic DNA following XbaI restriction endonuclease digestion were analysed by PFGE; this typing classified 56% of the 32 isolates recovered in 1996 into two major clusters. Cluster A included ten isolates from 1996 and three isolates recovered in 1995, whereas cluster B included eight isolates from the outbreak of 1996. The remaining isolates were genetically unrelated to those of clusters A and B; they constituted sporadic strains. The two major clusters were also evident using other molecular typing methods, such as random amplification of polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus (ERIC)-PCR, where isolates of clusters A and B could be identified on the basis of their discriminative patterns. This investigation showed the predominance of two epidemic strains, and illustrated the ease with which MRKP strains can disseminate and persist within a single ward.