The frequency of detection of Blastocystis hominis in the stools of patients with gastroenteritis is reported. Over a twelve-month period B. hominis was identified in the stools of 69 (4.72%) out of 1460 patients. Of these 69 positive samples, 45 (65%) contained B. hominis alone and in 24 (35%) it was present together with other parasites such as Lamblia intestinalis, Entamoeba histolytica, Entamoeba coli, Endolimax nana, Iodamoeba buetschlii, Ancylostoma duodenale, Ascaris lumbricoides, Trichuris trichiura, and Hymenolepis nana. In 19 of the 69 patients with B. hominis, the parasite was found only in small numbers but as the sole pathogen. It is still unclear whether B. hominis must be considered a pathogenic agent; the clinician should however be aware of this parasite as a possible cause of gastroenteritis, particularly when no other pathogen can be identified.