An outbreak of Candida glabrata fungemia that was thought to be associated with bottles used for milk feeds occurred at our children's infectious diseases clinic. This cluster of cases was investigated using a case-control study. Isolates were identified by conventional methods and karyotyped using pulsed-field gel electrophoresis (PFGE) of genomic DNA. Potential risk factors for nine hospitalized children with candidemia and 14 controls were long-term hospitalization and treatments with more than two antibiotics. Electrophoretic karyotyping showed a single chromosomal pattern for these outbreak isolates and, in addition, they all had the same antifungal susceptibility results. These findings suggest that clonal dissemination of a single strain was responsible for this outbreak. Karyotyping by PFGE appears to be a useful molecular typing method for strains of C. glabrata.