Open label study offering patients with steroid-refractory Crohn's disease an induction therapy with oral FK-506 plus 6-mercaptopurine. The medication FK-506 is an immunosuppressive agent utilized as an alternative to cyclosporine. Previous trials have suggested that 6- mercaptopurine may facilitate tapering of chronic steroids. The specific aims of this study are the evaluation of FK-506 plus 6- mercaptopurine in the therapy of pediatric Chrohn's disease unresponsive to steroid therapy. Evaluation is conducted on whether usage of FK-506 brings a more rapid improvement in diarrhea, anemia, and fistula closure than use of 6-mercaptopurine alone. The study will look at identification of immunologic abnormalities occuring in pediatric patients with Crohn's disease at the systemic and mucosal levels, and their response to therapy; including determination of serum and mucosal cytokine levels in active Chrohn's disease and their response to therapy, and analysis of peripheral blood lymphocyte subsets by flow cytometry while patients are on immunosuppressive medications. Evaluations will also be made on whether FK-506 therapy produces improvement in growth failure through steroid-sparing effects and treatment of Crohn's disease.