Résumé : Background and aims: Adalimumab is efficacious in inducing and maintaining remission in Crohn's disease but dose escalation is needed in 30-40% after 1. year. Attempts for dose de-escalation have not been studied. This study aimed to assess the need for, predictors, and outcome of dose escalation and de-escalation in a large cohort of adalimumab treated Crohn's patients. Methods: All consecutive patients treated with open label adalimumab for active Crohn's disease from the participating centres were included in this cohort study. A detailed retrospective chart review was performed to look for possible factors predicting outcome. Results: Eighty four percent of 720 patients had a primary response and were followed up for a median of 14. months. Thirty four percent needed escalation after a median of 7. months (0-55. months). Multivariate predictors for dose escalation were the following: prior anti-TNF use (p< 0.0001), no concomitant azathioprine or < 3. m (p< 0.02) and abnormal CRP at start (p< 0.05). Dose escalation re-induced response for at least 6. months in 67%. Only abnormal CRP at start correlated with failure of dose escalation (p= 0.02). Dose de-escalation was attempted in 54% and was successful in 63%. After a median follow-up of 14. m adalimumab was discontinued in 29% of patients. Conclusion: In this study real life nationwide cohort of Crohn's patients treated with adalimumab dose escalation was needed in 34% and was successful in 67%. Dose de-escalation was attempted in 54% and was successful in 63%. Overall 71% of patients maintained long term response on adalimumab. © 2012 European Crohn's and Colitis Organisation.