Ten patients with active Behçet’s disease were studied to evaluate whether the cutaneous response to intracutaneous injection of autologous plasma differs from those known to occur in the disease following needle prick and injection of normal saline (pathergy). No specific response to plasma was noticed. 8 of the 10 patients tested reacted positively to all 3 stimuli, and the remaining 2 developed no reaction to any of them. The reaction to plasma in a given patient was clinically identical to those produced by normal saline and needle prick. The only histological difference noticed was the prevalence of acute inflammation and perivascular granulocytic infiltrate at the sites of plasma. None of the reactions revealed thrombosis or necrosis of the blood vessels, and those minor vascular affections noticed seem to be secondary to the inflammatory process.