SummaryA systematic research of Yersinias in coprocultures on desoxycholate-citrate-lactose medium led to the isolation of a new strain of Yersinia enterocolitica from a 1 1/2 year old child (18th human case) with enteritis, which is more frequent with this germ than with the related Pasteurella pseudo-tuberculosis (B. of Malassez-Vignal). The seroagglutination test was also positive with the patient’s sister serum, for whom it allowed a retrospective diagnosis. The familial character of the infection should be noted. Although the cnteritic syndromes are predominant, Yersinia enteracolitica may also cause the same clinical forms as does the Malassez-Vignal bacillus : mesenteric adenitis, septicaemia, erythema nodosum, peripheric adenitis, etc. This clinical diversity, and the difficulty of the biological diagnosis are believed to explain the apparent rarity of this infection.