The efficacy of adalimumab in inducing and maintaining remission in both adults and children with moderate-to-severe Crohn's Disease has been demonstrated in multiple clinical trials. Despite efforts to optimize treatment, approximately 40% of patients who initially respond to anti-TNF ultimately lose response. Measurement of adalimumab (ADA) drug levels and antibodies to adalimumab (ATAs) in patients has been shown to assist decision making in patients who have lost response during the course of treatment. This approach is based on the observations showing that higher ADA concentrations are associated with higher treatment efficacy and that loss of response is primarily attributed to either undetectable drug levels or to the presence of high titers of ATAs. Existing data is mostly based on retrospective cohort studies, nevertheless, the concept of routine therapeutic drug monitoring in-order to improve efficacy is still evolving. Recently, preliminary results of the Trough level Adapted infliXImab Treatment (TAXIT) study, performed in adult IBD patients, have failed to demonstrate superiority of level-based treatment over clinically-based treatment regarding rates of response over time. Nevertheless, it is premature to conclude that patients do not benefit from a tailored approach as the reported abstract did not stratify patients according to type of disease (CD vs. ulcerative colitis) and as some significant advantages such as reduced rate of antibodies and reduction of CRP were described in the level-based arm. Anti-TNF treatment in pediatric patients may differ from adults due to a higher risk for developing the rare hepatosplenic T cell lymphomas (HSCTL) in young males treated with combination therapy including thiopurines and anti-TNF agents. Concomitant therapy (using immunomodulators, mainly azathioprine) which has demonstrated superiority over mono-therapy has become a standard of care in moderate to severe CD in adults. In-view of the concerns of pediatric gastroenterologist from concomitant therapy-induced adverse events the option to improve efficacy of mono-therapy by guiding it according to drug monitoring is further appealing. Therefore, our aim is to assess the efficacy of routine therapeutic drug monitoring based treatment in pediatric CD patients in a prospective randomized control trial. We hope that this study will further contribute to the understanding of the potential benefits of therapeutic drug monitoring based management in pediatric patients treated with anti-TNF agents.Hypothesis: