Irritable bowel syndrome (IBS) is still an ambiguous disorder of the gastrointestinal function. Several theories have been postulated as regard its underlying patho-physiology. Infection with intestinal parasites has been evaluated as a possible etiology with contradictory results. This study compared IBS cases with normal population in Fayoum Governorate as regard infection with parasites, and to detect their possible associated risk factors. Stool samples were parasitologically
examined by concentrated sedimentation, stained with Lugol's iodine, trichrome. The RIDA®QUICK Cryptosporidium/Giardia/Entamoeba Combi kits were applied. Stool samples were cultured on Jones and Loeffler's slope media for detection of Blastocystis spp. & D. fragilis, respectively. Blastocystis spp., D. fragilis & Cryptosporidium were the commonest parasites in the examined samples. Blastocystis spp. was the only parasite significantly associated with IBS. Contact with animals was a common risk factor for the three prevalent parasites. Low socioeconomic standard was a risk for Blastocystis & Cryptosporidium infections as well as consumption of contaminated food and/or drink was associated with Blastocystis infection.