Infections of the intestinal tract with Yersinia enterocolitica and Yersinia pseudotuberculosis are known the world over. Post-infection reactions like arthritis, erythema nodosum, erythema multiforme, scarlatiniform exanthemata and septicemic types deserve particular clinical attention. The clinical importance of enteric yersinioses has been shown in studies with the identification of significant antibody titers against Yersinia enterocolitis and Yersinia pseudotuberculosis in 6.71 and 4.58% respectively of 4411 patients examined for the first time. It was possible to isolate Yersinia enterocolitica from 5.05% of 616 samples of stool and Yersinia pseudotubercolosis from 0.66% of 136 lymph nodes taken from 751 patients.