Crohn's disease (CD) in childhood is a chronic relapsing and remitting condition that has a significant impact on growth and development. The disease is characterized by an increased and unregulated immune response. The main therapy over the last 30 years has been corticosteroids leading to remission in 50-80% of patients within 2-4 weeks. However, the use of steroids in children is limited by side-effects including acne, moon-face, hirsutism, hypertension, metabolic disturbances and above all reduced growth. Hence, pediatricians are very interested to find alternative therapies. Therapeutic manipulation of gut flora with probiotics promises to be a useful strategy for several disorders including inflammation of the gut. The efficacy of the highly concentrated probiotic VSL#3 has been documented in maintenance and prophylaxis treatment of pouchitis in double blind, placebo controlled studies in adults. The aim of this study is to compare probiotic therapy with VSL#3 versus placebo in maintenance therapy of children with mild to moderate CD, treated with either 5-ASA, corticosteroids (local or budesonide), imuran/6 mercaptopurine (MP), as long as no change in medication dosage has been made in the previous 12 weeks (for imuran/6MP) or 4 weeks (for corticosteroids).