The prevalence of Dientamoeba fragilis in patients from a metropolitan area in Denmark was determined by examination of paired stool samples using two techniques: a formol ethyl-acetate concentration technique with unpreserved faeces and a permanent staining technique on faeces preserved with sodium acetate-acetic acid-formalin (SAF). Using the SAF permanent staining technique and the formol ethyl-acetate concentration technique, 25% and 15% of the specimens, respectively, were parasite-positive. D. fragilis was detected in 12 of the 103 patients, only two of whom harboured other recognised pathogenic parasites. Overall, D. fragilis had a remarkably high prevalence in the metropolitan area of Denmark investigated.