Background Infliximab dependency in children with Crohn's disease (CD) has recently been described and found to be associated with a decreased surgery rate. Aim To assess infliximab dependency of adult CD patients, evaluate the impact on surgery, and search for possible clinical and genetic predictors. Methods Two hundred and forty-five CD patients treated with infliximab were included from Danish and Czech Crohn Colitis Database (1999-2006). Infliximab response was assessed as immediate outcome, 1 month after infliximab start: complete, partial, and no response. Three months outcome, after last intended infusion: prolonged response (maintenance of complete/partial response), infliximab dependency (relapse requiring repeated infusions to regain complete/partial response or need of infliximab > 12 months to sustain response). Results Forty-seven percent obtained prolonged response, 29% were infliximab dependent and 24% nonresponders. The cumulative probability of surgery 40 months after infliximab start was 20% in prolonged responders, 23% in infliximab-dependent patients and 76% in nonresponders (P <0.001). The cumulative probability of surgery at 40 months in patients on maintenance versus on demand regime was 33 and 31%, respectively (P = 0.63). No relevant clinical or genetic predictors were identified. Conclusion The infliximab dependency response seems to be equivalent to the prolonged response in adult CD patients when comparing surgery rates. Eur J Gastroenterol Hepatol 22: 1196-1203 (C) 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins