Objectives: To examine the effect of prophylaxis therapy on clinical and endoscopic disease recurrence in children with Crohn's Disease (CD) following ileo-cecal resection. Hypothesis: Post-operative pediatric patients treated with anti-Tumor necrosis factor (TNF) prophylaxis will demonstrate lower endoscopic recurrence rates at 1 year and lower clinical recurrence rates at 2 years compared with thiopurines treated patients. Design: A multi-center, prospective, observational study. Patients with either thiopurines or anti-TNF prophylaxis will be enrolled 0-6 months following ileo-cecal resection. Prophylactic treatment will be decided at the discretion of the treating physician and not as a part of the study. According to standard-of-care, patients will undergo a colonoscopic evaluation 6-9 month following surgery. Study visits will be performed at 6 months following resection, 12 months, 18 months and 24 months. Setting: Porto group and IBD interest group pediatric gastroenterology centers. Participants: Children 6 year to 18 years (Overall, 84 patients) with CD following limited ileo-cecal resection. Main outcome measure: 1. Endoscopic recurrence at 1 year (according to Rutgeerts Score: i2-i4). 2. Clinical recurrence at 2 years (according to pediatric Crohn's disease activity index-PCDAI: ≥10). Secondary outcome measures: 1. Re-operation rate at 2 years. 2. Exacerbation-free quartiles at 2 years. 3. Anthropometric and laboratory measures including calprotectin at each visit. 4. Changes in fecal microbiome- baseline, 1 year and 2 years. Inclusion criteria: 1. CD with phenotypes L1 and L3 following ileo-cecal resection. 2. No active perianal disease. 3. Prophylactic therapy with either thiopurines or anti-TNF. Exclusion criteria: 1. Pregnancy. 2. Active perianal disease (draining fistula or abscess). 3. Post-operative intra-abdominal complication (fistula or abscess). Sample size: In order to demonstrate 20% difference in endoscopic recurrence rate between groups is significant, we will need to study 42 children in each group to be able to reject the null hypothesis that the failure rates between the groups are equal with probability (power) of 80% and a type I error probability of 0.05.