Infections linked in time and space with Yersinia enterocolitica (serovar 0 : 9, biotype 2, lysotype X3) were observed in 6 cases within one university hospital. After a hospital epidemic in Finland in 1973 (involving 7 persons) this is the 2nd such observation. The spread was demonstrated in two areas. The probable source of infection of one patient group (n = 3) was a 48-year-old dialysis patient admitted with a febrile condition without enteritic symptoms. Pathogens could be demonstrated in his faeces by direct culture, in two contact persons cultivation was possible only with cold enrichment. Blood cultures of the first patient were negative. At about the same time 3 further infections with Yersinia enterocolitica of the same characteristics were observed in hospital personnel from different units. Frequent exchange of staff and patients among affected wards increases likelihood of cross-infection. A dialysis nurse with Yersinia arthritis was the possible link between patients and personnel. Transference of infection from one person to another can be assumed in the above cases.