Introduction: Irritable bowel syndrome (IBS), though a benign disorder is highly prevalent and imposes high cost and substantial morbidity upon general population. Long considered as functional disorder, IBS pathogenesis carries an organic basis at least in a subset of patients. Altered intestinal immune response and low grade intestinal inflammation have been confirmed as pathophysiology of IBS in few studies. Oxidative stress indicates that there is inflammation and, markers of oxidative stress may be developed as diagnostic tool for IBS in future. Study aimed to evaluate oxidative stress in form of total oxidant status (TOS), total anti-oxidant status (TAS), oxidative stress index (OSI) and serum prolidase activity (SPA) as a marker of intestinal inflammation in IBS patients and healthy controls. Material and methods: In this case -control study done at a teaching medical institute in north India over a period of one year, 120 IBS patients (cases) and 40 healthy volunteers (controls) were evaluated for TOS, TAS, OSI and SPA. Patients with IBS were sub-divided into 3 groups (40 each): diarrhea predominant, constipation predominant and mixed type (IBS-D, C and M respectively). Student t-test, chi-square test and ANOVA tests were used for statistical analysis. Results: Mean TOS, TOS/TAS (OSI) and prolidase levels were significantly higher in IBS group than control with p value of <0.001,< 0.001, and <0.01 respectively. Level of TOS was highest in IBS-D subgroup followed by IBS-M and Lowest in IBS-C subgroup showing a significant difference between IBS-D and IBS-C, IBS-D and IBS-M and IBS-M and IBS-C with p values <0.001 for each comparison. OSI was highest in IBS-D and lowest in IBS-C with significant differences between the subgroups (P<0.001). Only IBS-M subgroup had significantly higher serum prolidase activity when compared to controls (p<0.001) IBS-D (P=0.013) and IBS-C (P=0.01). TAS level was significantly higher in controls (P<0.001) than cases. There were significant differences between all four subgroups (p<0.001) except between IBS-C and IBS-M subgroups (P=0.294). Conclusion: This study observed that there is increased oxidative stress and decreased antioxidant capacity in patient with IBS. To support our results further prospective and randomized controlled trials are necessary.