Self-focused attention has been linked to social anxiety and poor social performance, but the causal direction of this relationship has not been established. For this study, focus of attention was manipulated during a speech task, conducted in pairs for 38 individuals with generalized social phobia. Results indicated that intensifying self-focused attention increased anticipated anxiety and anxious appearance, regardless of whether the individual was giving a speech or passively standing before the audience. The self-focus manipulation also increased self-reported anxiety during the task, but only for individuals assigned to a passive role. Contrary to expectation, self-focused attention did not affect any measure of social performance. These results indicate that self-focused attention may play a causal role in exacerbating social anxiety.