BACKGROUND/RATIONALE:||Treatment outcomes of patients with inflammatory bowel disease (IBD) have improved enormously during the past decade due to the use of anti-tumour necrosis factor (anti-TNF) therapy. As a result, 67 to 91% of paediatric patients and 66% of adult patients is still in sustained remission two years after the initiation of anti-TNF therapy. Prolonged use of anti-TNFs comes with disadvantages such as dose dependent susceptibility to infections and dermatological adverse effects. Preliminary, mostly uncontrolled studies suggest that dose reduction by dosing interval lengthening is a realistic option in a relevant proportion of patients with IBD, provided that intensive follow-up is applied.||OBJECTIVE:||To evaluate whether a faecal calprotectin (FC) guided strategy of anti-TNF dosing interval lengthening is non-inferior in maintaining remission in patients with IBD, compared with an unchanged dosing interval.