Crohn's disease (CD) and ulcerative colitis (UC), the two idiopathic inflammatory bowel diseases (IBDs), affect almost two million individuals in North America and several million worldwide. Cytokines are important in the pathogenesis of CD, and their manipulation has successfully reduced disease severity and maintained remission. Following the discovery of novel cytokines and the role they may play in gut mucosal immunity, as well as the emergence of new concepts and changing paradigms in CD pathogenesis, the roles of several cytokines have been elucidated and tested in both preclinical animal models and clinical trials of patients with IBD. Complementary to this, proof of concept for new cytokine targets is rapidly developing, with the possibility of future cytokine-based therapies that may offer greater specificity and decreased toxicity for the treatment of CD. This review discusses novel concepts in CD pathogenesis and the roles of cytokines in the initiation and perpetuation of disease. In addition, we review applications of cytokine-based therapies in human clinical trials and preclinical animal studies. Finally, we discuss novel cytokine targets not yet investigated in vivo and describe their potential contribution to CD pathogenesis.