BACKGROUND Plesiomonas shigelloides is a common pathogen in tropical regions, whereas it is rarely isolated in temperate climates. It is most often found in surface water and fish. During the last 10 years it was found to cause gastroenteritis 6 times in Ludwigshafen. Not all of these patients reported a trip to foreign countries. METHODS A 54-year-old male patient was hospitalized after a trip to Malaysia with strong greenish watery diarrhea and chills. On physical examination we saw a dehydrated patient in severely reduced general condition. The stool frequency was 30/d. The laboratory examinations only showed elevated parameters of inflammation. Plesiomonas shigelloides was cultivated in the stool cultures. With appropriate substitution of fluid and electrolytes, and antidiarrheal therapy the patient resumed a normal diet without any complications. Three days later his bowel movements were normal and his general condition was greatly improved. We withheld antibiotic therapy because of the noncomplicated course of illness. CONCLUSIONS In Germany infections with Plesiomonas shigelloides are rare, an increase is observed because of increasing tourism to tropical regions. The course of infection is sometimes asymptomatic, but usually patients develop an acute gastroenteritis. Especially immunocompromised patients can show serious courses of infection. Plesiomonas shigelloides should be included in the differential diagnosis of acute gastroenteritis after journeys to tropical regions. Some of our patients, however, denied traveling to tropical regions. They also denied consuming seafood, which indicates a risk of infection in Germany. Still an infection with Plesiomonas shigelloides seems to be rare in northern European countries.