This study reviews research on the construct of intolerance of uncertainty (IU). A recent factor analysis (Journal of Anxiety Disorders, 25, 2012, p. 533) has been used to extend the transdiagnostic model articulated by Mansell (2005, p. 141) to focus on the role of IU as a facet of the model that is important to address in treatment. Research suggests that individual differences in IU may compromise resilience and that individuals high in IU are susceptible to increased negative affect. The model extension provides a guide for the treatment of clients presenting with uncertainty in the context of either a single disorder or several comorbid disorders. By applying the extension, the clinician is assisted to explore two facets of IU, "Need for Predictability" and "Uncertainty Arousal."