The study will evaluate the possible efficacy of 2-chlordeoxyadenosine (2-CdA) in patients with Crohn's disease refractory to steroid therapy or those requiring long-term, high-dose steroids. It is hypothesized, with preliminary data, that this drug may be effective against the chronic inflammatory process that characterizes Crohn's Disease and may provide lower toxicity than traditional immunosuppressive therapies. This will be tested in a double-blind, randomized, placebo-controlled trial.