Yersiniosis is mentioned as a zoonotic infectious disease and its course might be surprising and unpredictable. Severe diarrhea and crumping abdominal pain are the most common symptoms of infection and if not treated it may cause plenty of complications such as joint swelling and skin changes (erythema nodosum).The aim of the study was to analyze the clinical course and reaction to administered drug therapy in correlation with laboratory and ultrasound findings in patients with serologically confirmed yersiniosis.The retrospective analysis included 10 children with yersiniosis, hospitalized in Department of Pediatric Cardiology and Rheumatology from 2010 to 2012. Demographic data, initial diagnosis, characteristics of clinical symptoms, laboratory tests and reaction to administered treatment were analyzed.Half of the analyzed group of children had an episode of vomiting and abdominal pain in the past, but only one of them had severe symptoms of gastroenteritis at the certain time. Joint discomforts appeared in the majority of patients in the analyzed group so that the inflammatory connective tissue disease was suspected. During control hospitalizations (few weeks after antibiotic treatment) persisting high titer of anti-Yersinia antibodies had been observed among the children, as the second course of antibiotic therapy was needed.The authors emphasise the significance of the early diagnosis, antibiotic treatment and different – out of gastrointestinal – clinical manifestation of this disease.