Chronic or recurrent abdominal pain constitutes a serious diagnostic and therapeutic problem in childhood. The gastrointestinal, biliary tract or renal lesions often produce the chronic abdominal pain in children. Among causative factors of the chronic abdominal pain the infection with Giardia lamblia is more and more often taken into account. The sample of 112 patients hospitalized during the period from 1992 to 1993 in two departments of the University School of Medicine in Białystok and in three pediatric wards of the Municipal Hospital in Białystok, was assessed. In all children the duodenal aspiration was performed. The following questions were evaluated: 1. What is the frequency of giardiasis in children coming from north-east Poland and presenting chronic abdominal pain? 2. Is there any specific spectrum of symptoms of giardiasis in children? Based on the results of the duodenal fluid examination, the infection with G. lamblia was diagnosed in 77 (67.75%) children. The analysis of the clinical symptoms indicated that only failure to thrive and recurrent episodes of the loose stools were significantly more frequent in infected children compared with uninfected. The frequency of the other symptoms like nausea, headache, vomiting, constipation, fever or allergic skin lesions was similar in both study groups.