Blastocytis hominis has long been described as a non-pathogenetic protozoan parasite until recently, when claims have been made that it could be the cause of intestinal disorders. The clinical picture of B. hominis consists of non specific abdominal pain, watery diarrhea, anorexia, vomiting and weight loss. Rarely a more invasive form of the disease with rectal bleeding can occur. We describe the case of a ten year-old girl who was admitted to our hospital for diarrhea, abdominal pain and fever. The presence of B. hominis was demonstrated in her stools. The patient responded favourably to treatment with metronidazole. We feel that our observation is an additional support to recognition of B. hominis as a human pathogen.