The objective of this study was to investigate the prevalence of intestinal parasites and the possible association between irritable bowel syndrome (IBS) and parasitic infections. The study included 100 IBS patients and 100 healthy control subjects. All study subjects filled a structured questionnaire, which covered demographic information and clinical data. Fresh stool samples were collected from patients and control subjects and processed during the same day of collection. Iodine wet mounts and trichrome stained smears prepared from fresh stool and sediment concentrates were microscopically examined for intestinal parasites. Patients attended private gastroenterology clinics and those found to have IBS (45 males and 55 females) were then selected in this study. The healthy subjects (50 males, 50 females) were recruited as controls. In the IBS patients, Blastocystis sp. was detected in 57% and Giardia sp. cysts were observed in 43%. In the control subjects, Blastocystis sp. was detected in 12% and Giardia sp. cysts were observed in 20%. These parasites were found either alone or with other parasites. Only the differences in the presence of Blastocystis (P=0.0001) and Giardia (P=0.0006) between IBS patients and controls were statistically significant. Abdominal pain and blotting were the leading symptoms in IBS patients and controls. Prevalence of Blastocystis and Giardia was higher in IBS patients than in controls. These parasites are likely to have a role in the pathogenesis of IBS. The findings of the study support a possible link between parasitic infections and IBS.