Binding parameters of the alpha 2-adrenoceptor (using [3H]yohimbine) and the 5-HT uptake site (using [3H]imipramine) were measured in intact platelets in a group of 15 patients with a DSM-III diagnosis of panic disorder. When compared with an age- and sex-matched control population no differences in either Bmax or Kd were found. This result is discussed in light of the reports of platelet binding abnormalities in depression.