BACKGROUND & OBJECTIVE: Western studies show that up to 65 per cent of patients with Crohn's disease have low serum 25-hydroxy vitamin D concentrations, and 45 per cent of these patients have metabolic bone disease. No data are available from India or from any country with comparable climatic conditions or ethnicity. We carried out this study to measure the serum 25 (OH) vitamin D levels of Crohn's disease patients and compare with matched controls and to assess the consequences of low 25 (OH) vitamin D levels on bone and mineral metabolism in these patients. METHODS: Adult patients with Crohn's disease were compared with age and sex matched patients diagnosed to have irritable bowel syndrome. Serum 25 (OH) vitamin D, the effect of disease characteristics, sunlight exposure and milk consumption on 25 (OH) vitamin D level, and the consequences of low 25 (OH) vitamin D level on bone and mineral metabolism were assessed. RESULTS: Thirty four patients with Crohn's disease (M:F, 24:10, age 39.2 +/- 12.9 yr) and 34 controls (M:F, 24:10, age 38.9 +/- 13.4 yr) were studied. 25 (OH) vitamin D levels were significantly lower in patients with Crohn's disease as compared to controls (Crohn's disease vs controls: 16.3 +/- 10.8 vs 22.8 +/- 11.9 ng/ml; P<0.05). The severity of disease activity as assessed by the Harvey Bradshaw score correlated negatively (Correlation coefficient -0.484, significance P<0.004), and the duration of sunlight exposure correlated positively (Correlation coefficient 0.327, significance P=0.007) with the serum 25 (OH) vitamin D level. INTERPRETATION & CONCLUSION: Serum 25 (OH) vitamin D levels were significantly lower among patients with Crohn's disease as compared to age and sex matched controls. Further, 25 (OH) vitamin D levels in patients with Crohn's disease were lower in those with severe disease activity and less sun exposure. Further studies need to be done to correlate low 25 (OH) vitamin D level with bone density and assess the effect of vitamin D supplementation in these patients.