BACKGROUND: A diminished antioxidant defence and alterations in the fatty acid profile may play a role in the pathophysiology of inflammation in Crohn disease (CD). METHODS: Antioxidant status (serum antioxidant vitamins and minerals, glutathione peroxidase, and superoxide dismutase activity), disease activity, dietary intake, and the fatty acid profile in plasma and erythrocyte phospholipids were studied in patients with active CD (n = 12), inactive CD (n = 50), and controls (n = 70). Eight patients with active CD were re-evaluated during the subsequent phase of clinical remission. The relation between the variables was assessed by multiple linear regression. RESULTS: We observed a significantly diminished antioxidant status in patients with active CD compared with inactive CD and controls. Furthermore, the antioxidant defence was depleted in patients with inactive CD compared with controls. An aberrant fatty acid profile in plasma phospholipids was found in active and inactive CD compared with controls. Multivariate analysis showed that the plasma phospholipid fatty acid indices were significantly associated with several antioxidants (beta-carotene, vitamin E, and glutathione peroxidase) in CD patients but not in controls. CONCLUSION: The fatty acid profile in CD patients is significantly associated with disease activity and serum antioxidant concentrations. This observation, along with the diminished antioxidant defence in patients with active and inactive CD, indicates that antioxidants should be considered in the therapy of inflammation in CD.