The patient feels very sick. He is tired and apprehensive, his heart pounds and his breathing is labored. From time to time he is overcome by fright and the conviction that he is seriously ill or even about to die. Still, his doctor says: "There is nothing wrong with you." This is a description of someone with an anxiety neurosis, a chronic disorder that affects perhaps 5 percent of the U.S. population. Most physicians have been unable to recognize it, let alone treat it; its cause has seemed to be obscure and somehow "psychogenic." Yet in our laboratory at the Washington University School of Medicine we have been able to produce the symptoms of anxiety neurosis and even acute anxiety attacks in susceptible patients by chemical means: we administer enough lactate, a normal product of cell metabolism, to raise the blood lactate level about as high as it is in