Purpose: There is very limited data regarding the duration and dose of steroids required to produce bone loss in IBD. The objective of this study is to prospectively determine the rate and degree of bone loss in IBD patients treated with prednisone (pred), compared to a group of IBD patients matched for disease activity not treated with prednisone (non-P). Methods: Pred patients (n = 17) underwent baseline DEXA to determine baseline bone mineral density (BMD) at the lumbar spine (LS), and bilateral hips, and were compared to non-P patients (n = 15) with active disease. DEXA scans were repeated at 3 months after initiating prednisone, or alternate therapy, for non-P patients. Prednisone was started at 40–60 mg/d and tapered according to a fixed schedule based upon clinical response. All patients were treated empirically with oral calcium 1500 mg/d and vitamin D 600 u/d. Results: For pred patients compared with non-P patients, there were no differences in the gender (M:F = 11:6 vs 11:4), age (36 vs. 44), There was a lower proportion of CD patients in the pred group (3/17) than in the non-P group (12/15, p=.001). All women were premenopausal. Patients in both groups had similar baseline disease activity. Pred patients had higher t scores for both LS and hips at baseline. Values for baseline t scores, and 3 month changes in t score and% BMD are shown in the Table below. p values are for differences between the pred and non-P groups.TableThere was also a higher proportion of pred patients with a clinically significant, i.e >5%, decline in BMD at the hips, than in the non-P group (5/17 vs. 0/14, p=.04). Conclusions: In this prospective, controlled study, a < 3 month course of prednisone, led to a significantly greater decline in BMD at the hips (but not at the spine) compared to control patients at 3 months. Significant bone loss at the hips, as defined by a greater than 5% decline in BMD, can be seen as early as 3 months in these patients with active IBD being treated with a tapering course of prednisone, despite concurrent supplemental calcium and vitamin D.