A bleeding disorder, probably familial, with absent adrenaline-induced platelet aggregation and lack of secondary aggregation response to ADP and platelet activating factor (PAF), is described. The laboratory findings do not fit any hitherto recognized hemorrhagic disease. The disorder was not caused by alpha-adrenergic receptor deficiency, but the ultimate defect has not yet been unraveled. This patient illustrates that a normal response to more than one aggregating stimulus is necessary for normal hemostasis, and indicates a physiopathological role for adrenaline not hitherto recognized. Whether this also applies to PAF remains to be proven.