54 cases of erythema nodosum, seen in the Department of Dermatology at the St. Raphael University Hospital, Louvain, were reviewed for their possible aetiology. A search for Yersinia enterocolitica (Y.e.) agglutinins was performed in 21 patients of whom 8 had significant serum antibody titres. These cases are presented and discussed. Gastro-intestinal symptoms, preceding by 2 weeks the erythema nodosum, are strongly suggestive for an aetiologic link with Y.e. Our observations confirm and extend to this part of Europe, the experience of other, mainly Scandinavian, authors.