Clinical presentation at diagnosis and disease course of both Crohn's disease (CD) and ulcerative colitis (UC) are heterogeneous and variable over time. During follow up, intestinal strictures or perforation may eventually develop at most patients with CD, and significant number of patients will undergo surgery. Much emphasis was laid in recent years on the determination of important predictive factors. Since early introduction of immunomodulators and/or biologicals might be justified in patients at risk for disease progression, so it is important to identify these patients as soon as possible. This review article summarizes the available literature on important clinical, endoscopic, fecal, serological/routine laboratory and genetic factors and hopefully will assist clinicians in the decision making of daily practice when choosing the treatment strategy for their patients with inflammatory bowel diseases.