Clinical anxiety disorders and elevated levels of anxiety vulnerability are characterized by cognitive biases, and this processing selectivity has been implicated in theoretical accounts of these conditions. We review research that has sought to evaluate the causal contributions such biases make to anxiety dysfunction and to therapeutically alleviate anxiety using cognitive-bias modification (CBM) procedures. After considering the purpose and nature of CBM methodologies, we show that variants designed to modify selective attention (CBM-A) or interpretation (CBM-I) have proven capable of reducing anxiety vulnerability and ameliorating dysfunctional anxiety. In addition to supporting the causal role of cognitive bias in anxiety vulnerability and dysfunction and illuminating the mechanisms that underpin such bias, the findings suggest that CBM procedures may have therapeutic promise within clinical settings. We discuss key issues within this burgeoning field of research and suggest future directions CBM research should take to maximize its theoretical and applied value.