The Gardner-Diamond syndrome is a disorder characterized by recurrent spontaneous painful bruising in patients with underlying psychosis and neurosis. Despite the presence of other symptoms suggestive of an underlying disorder of primary hemostasis in a large percentage of reported patients, results of testing for von Willebrand disease or platelet function disorders are lacking. The authors describe a case of Gardner-Diamond syndrome in an adolescent girl who had abnormal platelet responses during platelet aggregation studies. A review of the literature revealed only three additional patients with Gardner-Diamond syndrome who have had platelet aggregation studies reported. To date, all patients with Gardner-Diamond syndrome reported to have undergone platelet aggregation studies have had abnormal results.