Klebsiella pneumoniae resistant to ceftazidime was isolated from six adult women and two neonates hospitalized between July and November 1993 in the Department of Obstetrics and Gynecology of Boucicaut Hospital (Paris, France). The epidemiological investigation revealed a notably short delay (less than 48 h) between admission and contamination of the six adults and peripartum transmission to the neonates. The only environmental source of ceftazidime-resistant K. pneumoniae was the ultrasonography coupling gel used in the emergency room. Phenotypic (biotyping and antibiotyping) and genotypic (plasmid profile and pulsed-field gel electrophoresis) analysis of all the clinical isolates indicated the spread of a single strain. It produced SHV-5 and TEM-1 beta-lactamases, as demonstrated by isoelectric focusing and gene sequencing. The risk of cross-contamination in ultrasonography procedures is usually low and had not been associated so far with bacteria producing an extended-spectrum beta-lactamase (ESBL). Furthermore, this is the first time an epidemic of an SHV-5 ESBL-producing member of the family Enterobacteriaceae has been reported from a French hospital.