Research suggests that individuals with generalized anxiety disorder (GAD) show an attention bias for threat-relevant information. However, few studies have examined the causal role of attention bias in the maintenance of anxiety and whether modification of such biases may reduce pathological anxiety symptoms. In the present article, the authors tested the hypothesis that an 8-session attention modification program would (a) decrease attention bias to threat and (b) reduce symptoms of GAD. Participants completed a probe detection task by identifying letters (E or F) replacing one member of a pair of words. The authors trained attention by including a contingency between the location of the probe and the nonthreat word in one group (Attention Modification Program; AMP) and not in the other (attention control condition; ACC). Participants in the AMP showed change in attention bias and a decrease in anxiety, as indicated by both self-report and interviewer measures. These effects were not present in the ACC group. These results are consistent with the hypothesis that attention plays a causal role in the maintenance of GAD and suggest that altering attention mechanisms may effectively reduce anxiety.