OBJECTIVE: This study compared dopamine D2 receptor binding potential in patients with social phobia and healthy comparison subjects. METHOD: Dopamine D2 receptor binding potential was assessed in 10 unmedicated subjects with generalized social phobia and no significant lifetime psychiatric comorbidity and 10 healthy comparison subjects matched for age and sex. Binding potential was measured in the striatum by using single photon emission computerized tomography and constant infusion of the D2 receptor radiotracer [123I]iodobenzamide ([123I]IBZM). RESULTS: Mean D2 receptor binding potential was significantly lower in the subjects with social phobia than in the comparison subjects. Within the social phobia group, there was a nonsignificant correlation of binding potential with the Liebowitz Social Anxiety Scale score. CONCLUSIONS: Generalized social phobia may be associated with low binding of [123I]IBZM to D2 receptors in the striatum.