SummaryBackground and objectives:
 Irritable bowel syndrome (IBS) is the most prevalent functionalgastrointestinal (GI) disorder, which presents with abdominal pain and changes in the bowelhabits. Although the exact cause of IBS remains uncertain, some studies have shown that theinflammation and cytokine imbalance may act as potential etiological factors. The aim of ourstudy is to compare the serum levels of interleukin 6 (IL-6), interleukin 8 (IL-8), and tumornecrosis factor-alpha (TNF-) in patients with IBS with the healthy controls. The other aimof this study is to evaluate possible association between above-mentioned cytokines and IBSsubtypes.Methods: Seventy-four IBS patients diagnosed based on Rome III criteria and 75 gender and age-matched healthy controls were included in this study. Cytokines were measured in the serumusing enzyme-linked immunosorbent assays (ELISA).Results: Patients were classified into groups of IBS with diarrhea (IBS-D): 34, IBS with constipa-tion (IBS-C): 29, and IBS with mixed symptoms (IBS-M): 11. The serum levels of IL-6, IL-8 andTNF- were significantly higher in patients with IBS as compared to controls (P < 0.001). Therewas no difference in serum levels of cytokines based on IBS subtypes