Over a period of four years 18 children seen in our clinic have been diagnosed as suffering from Yersinia enterocolitica reactive arthritis: this group constitutes one third of the total reactive arthritides seen by us. The diagnosis was based on elevated specific antibody titres and the outcome has always been good with anti-inflammatory therapy, symptoms disappearing within a few weeks without any complications or recurrences. This positive outcome could be due to the absence of the HLA B27 haplotype. Yersinia has been described as the most frequent agent causing reactive arthritis, a common complication in an otherwise benign infection in children. It seems that Yersinia may trigger in predisposed hosts an immunological reaction leading to arthritis.