From December 1994 to November 1995 an unusual accumulation of Listeria infections occurred at the University Hospital Hamburg-Eppendorf, Germany. Eleven immunosuppressed patients from different departments developed septicemia due to Listeria monocytogenes during hospitalization. In a retrospective study, serotyping and pulsed-field gel electrophoresis revealed that six isolates were identical or genetically related. Four of them had been isolated from renal transplant recipients. Listeria monocytogenes was neither detected in food samples of the renal transplantation ward, nor in stool specimens obtained from the ward staff. There had been no close contacts among the infected patients. Before transplantation, the renal transplant recipients had been dialysed in different dialysis centers. Nosocomial foodborne transmission could not be proven but seems likely.