Multiple biopsies from the lower duodenum were obtained during endoscopy of 171 patients with dyspepsia, diarrhoea and/or suspected malabsorption. Histological evidence of lambliasis was obtained in six (3.5%). Antibiotic treatment with metronidazole, 250 mg two or three times daily for seven to 11 days (which had to be repeated in two cases), improved symptoms in four. In most of the patients "functional upper-abdominal symptoms" had been diagnosed after extensive examinations. In case of unclear upper-abdominal symptoms, chronic or chronic-recurrent diarrhoea and/or malabsorption lambliasis should be considered and histological examination of the duodenal mucosa undertaken.