Complex perianal disease is associated with poor outcome and requires early effective therapy. Corticosteroids are not effective in perianal fistulising Crohn’s disease, and antibiotics, immunosuppressants and anti-TNF therapy are required. It is important to consider combined medical surgical therapy after accurate imaging using an MRI scan of the pelvis. Drainage of any abscess at examination under anaesthesia and seton insertion are important before introduction of immunosuppressants and anti-TNF therapy. Long-term follow up of patients in a single centre reported responders to azathioprine having a reduced risk of perianal surgery (OR = 0.36; 95% CI: 0.27-0.46), but complex perianal fistulising Crohn’s disease generally requires combination therapy with anti-TNF and azathioprine.