Background: Although suggested, it has never been convincingly documented that food sensitivity is of pathogenetic importance in chronic inflammatory bowel disease. However, many patients may relate their gastrointestinal symptoms to specific food items ingested and may restrict their diet accordingly. Methods: A questionnaire was sent to all patients with chronic inflammatory bowel disease who attended the outpatient clinic, Medical Dept., Roskilde County Hospital in Koge, Denmark, in the year 1993. The patients were asked whether they had problems with any particular food item and, if so, to describe the symptoms experienced from it. A control group of 70 healthy persons were included. Results: Among 189 patients, 132 (70%) responded. One hundred and thirty had completed the questionnaire, 52 males and 78 females aged 13-89 years (median, 43 years). Fifty-three (41%) had Crohn's disease (CD), 69 (53%) ulcerative colitis (UC), and 8 (6%) unclassified colitis. Forty-one patients (31 CD, 10 UC) were operated on; 51 (19 CD, 32 UC) had disease activity. Sixty-five per cent of the patients and 14% of the controls reported being intolerant to one or more food items (P <0.0001). The intolerance covered a wide range of food products. The commonest symptoms among patients were diarrhoea, abdominal pain, and meteorism and among controls, regurgitation. Food intolerance was equally common in CD (66%) and UC (64%) and was not related to previous operation, disease activity or disease location. Conclusion: Most patients with chronic inflammatory bowel intolerance disease feel intolerant to different food items and may restrict their diet accordingly. The frequency and pattern of food intolerance did not differ between patients with CD and UC. The food intolerance was probably unspecific rather than of pathogenetic importance.