OBJECTIVES: Fatty acid metabolism is involved in the immune response and inflammation processes in patients with Crohn's disease (CD). Fatty acid changes may be relevant to the clinical course of the disease. The aim of this study was to compare the qualitative and quantitative fat intake and fatty acid composition of plasma phospholipids and adipose tissue in a defined population of CD patients with those in matched controls. METHODS: Dietary fat intake and fatty acid profile of plasma phospholipids and adipose tissue were assessed in two patient populations: 20 patients with recently diagnosed CD and 32 patients with longstanding (> 10 yr) CD clinically in remission, matched for age and gender with healthy controls. RESULTS: We observed no significant differences in quantitative or qualitative fat intake between CD patients and controls. Percentages of linoleic acid and alpha-linolenic acid in plasma phospholipids or adipose tissue were not significantly different between patients and controls. However, we observed a significantly (p < 0.05) lower percentage of the sum of the n-3 fatty acids, with significantly (p < 0.01) higher levels of clupanodonic acid (22:5n-3) and significantly (p < 0.05) lower levels of docosahexaenoic (22:6n-3) and arachidonic acid (20:4n-6). The aberrant fatty acid profile was more evident in patients with longstanding CD than in patients with recently diagnosed CD. CONCLUSION: The aberrant fatty acid profile found in these CD patients is a result of altered metabolism rather than of essential fatty acid malabsorption. The reported findings may be important in the pathophysiology of CD and hence in the choice of fatty acids to be used when therapeutic supplementation is considered in CD patients.