Osteoporosis is frequent in Crohn's disease. The aim of the study was to assess the rate of bone loss over time retrospectively and the influence of disease-related factors on bone loss. Twenty-nine patients (8 male), admitted for repeated bone mineral density assessments (BMD) were enrolled. BMD measured by dual energy x-ray absoptiometry was expressed in grams per square centimeter, and as sex- and age-matched Z score. The mean interval between BMD assessments was 41 months, during which period 27 patients used corticosteroids (mean dose 8.6 g) and 21 patients some form of bone protective medication. Initial Z scores at a mean age of 41 years were significantly below zero (spine -1.6 +/- 1.4; femur -1.4 +/- 1.4). Over time, no change in absolute BMD was observed accompanied by an improvement in Z scores. At the same time, an increase in body weight and a decrease in erythrocyte sedimentation rate (ESR) was observed. Multilinear regression analysis demonstrated change in ESR as independent predictor for change in femoral Z score. In conclusion, low BMD is frequent in Crohn's disease, but decline of BMD over time was not found, despite ongoing use of corticosteroids.