A woman had episodic attacks of flushing associated with severe skin, bone, and abdominal pain, accompanied by mood alterations and anxiety, and followed by an organic psychosis. These symptoms and signs could be induced by small doses of clonidine, L-5-hydroxytryptophan, pentagastrin, insulin, epinephrine, compound 48/80, methacholine, morphine, histamine, or d-tubocurarine. Skin testing showed abnormally sensitive mast cells and an exaggerated axon flare. Cimetidine initially prevented the attacks but became less effective after 18 months. Thyrotropin-releasing hormone stopped the skin pain whereas neurotensin reproduced the burning sensation in the skin without inducing the attack. Both the flush and the organic psychosis were reversed entirely by naloxone or naltrexone, and the hallucinosis could be reversed by vasodilators.