BACKGROUND Bacillus cereus can cause severe infections in immunocompromised persons. METHODS We report 3 cases of bacteremia/septicemia (1 fatal) among oncology patients in a children's hospital. Because all cases occurred during a 10-day period, a common source outbreak was suspected. An epidemiologic investigation was performed. Molecular comparison of patient and environmental isolates was performed by using pulsed-field gel electrophoresis. RESULTS After an extensive investigation, no common hospital source could be found. Pulsed-field gel electrophoresis proved that the isolates were not related. CONCLUSION Sporadic infections in immunocompromised persons do occur and can be associated with significant morbidity.