Aim 1: To obtain clinical parameters of disease activity, biochemical markers of bone turnover and serum levels of selected cytokines (IL-6, IL-1b, TNF-a) in patients with inflammatory bowel disease (IBD). These variables will then be individually correlated with bone density to find which patients are at increased risk for osteopenia. The clinical measurements will be followed prospectively over a period of 2 years at 6-month intervals. These data will complement and expand the limited available information on bone homeostasis in children with Crohn's disease (CD). Sera from these patients will be used for basic laboratory experiments (Aim 2). Aim 2: To determine which cytokines in the serum from CD are involved in decreasing bone formation. Antibodies to specific cytokines (IL-6, IL-1b, TNF-a) will be applied to the mineralizing organ culture system to block the inhibition of calcification and assess which cytokines are causing bone alterations. Havingt identified the candidate cytokines by this approach, we will add each candidate cytokine in clinically relevant concentrations to the organ culture system and to an osteoblast cell culture system to confirm their role in osteopenia.