Beta-adrenergic receptor kinetics were measured in leukocytes from 17 drug-free, nondepressed patients with social phobia (generalized type) and 17 gender-matched and age-matched healthy controls. Binding was characterized using the highly specific beta-adrenergic ligand [125I]pindolol (125IPIN). Contrary to some studies in panic disorder and many studies in depression, no significant difference was found in Bmax or Kd values between social phobic patients and controls. Neither severity of social phobic symptoms nor the severity of certain symptoms of beta-adrenergic activation (i.e., tachycardia, tremor, blushing) influenced Bmax or Kd. To the extent that these peripheral indices can be considered reflective of central processes, these findings suggest that a simple defect in beta-adrenoceptor number of affinity is unlikely to explain the pathophysiology of generalized social phobia.