Legionella pneumophila serotype 6 was isolated from the peritoneal fluid of a 59-year-old immunosuppressed patient who developed peritonitis shortly after kidney transplantation. Clinical and radiological examination did not show pulmonary abnormalities until shortly before his death when multiple organ failure developed with adult respiratory distress syndrome (ARDS). Post mortem examination showed L. pneumophila in the peritoneum and in a small pulmonary infiltrate, confirmed by positive cultures. A primary peritoneal inoculation via an indwelling Tenckoff catheter seems to have been the most likely route of infection. Positive L. pneumophila type 6 cultures were obtained from the shower and hot water tap in the room of the patient. L. pneumophila must be considered as a potential cause of peritonitis in which routine microbiological cultures remain negative.