A nosocomial cluster of Candida guillermondii fungemia ( n=5 episodes) occurred in a surgical unit over a 2-week period. The five infected patients had received parenteral nutrition through central lines and three of them had catheter-related candidemia. All of the isolates were resistant to 5-flucytosine (MIC >32 microg/ml) and they had strictly related fingerprints, as generated by randomly amplified polymorphic DNA analysis. Although no isolate of Candida guillermondii was recovered from other clinical, surveillance or environmental samples, nosocomial spread of this yeast stopped following the reinforcement of infection control measures. Candida guillermondii may require an intravascular foreign body to cause fungemia, but the outbreak reported here shows that it can be transmitted nosocomially and cause epidemics.