A 6-year-old boy with non-Hodgkin's lymphoma presented because of recurrent episodes (on 13 September 1993 and 12 January 1994) of possibly catheter-related bacteremia. The strains isolated during both episodes and seven epidemiologically unrelated control strains were typed by pulsed-field gel electrophoresis (PFGE) of chromosomal DNA. The similarity of the PFGE patterns of the two isolates suggests that both episodes of bacteremia were caused by the same strain. The antimicrobial susceptibility of the nine strains was tested against 32 antimicrobial agents. The antimicrobial susceptibility patterns of the two isolates from the referred case were identical and differed from those of other clinical isolates. The best in vitro activity (associated with 100% susceptibility) was demonstrated by ofloxacin, clinafloxacin, minocycline, and rifampin.