Osteopenia and osteoporosis are prevalent in patients with Crohn's disease (CD). We conducted a cross-sectional study on consecutive patients with CD to assess the prevalence and factors associated with low bone mass density (BMD). One hundred sixty-eight patients with CD were evaluated. Baseline demographics, medical and surgical history, calcium intake, physical activity, steroid use, Harvey Bradshaw Index, blood and urine tests, and dual-energy X-ray absorptiometry were obtained. Sixty-seven (40%) and seventy-five (45%) patients had osteopenia of the femur and spine, respectively. Ten to 11% of patients had osteoporosis. Of the 40 patients who never used steroids, 19 (48%) had osteopenia of the femur and 12 (30%) of the spine. Significant associations were found between BMD and age, body mass index, and serum magnesium. Lifetime steroid use was a weaker predictor of bone loss. Duration of disease did not correlate with BMD when adjusted for age. At follow-up at a mean of 2 years, BMD declined in the femur but not the spine. However, those with ongoing steroid use had lower spine BMD. A significant number of patients with CD have osteopenia. Age was the most important predictor of bone loss. Significant proportion of steroid naive patients had osteopenia, which implies that mechanisms other than steroid use are also involved in bone loss in CD. Disease activity, systemic inflammation, and hormonal and genetic factors may all be important determinants of bone loss in CD.