The Centers for Disease Control received a request through the US Department of State to provide physicians to investigate a health problem on the West Bank. The following are the findings. From March 21 to April 3, 943 cases of an acute, non-fatal illness characterized by headache, dizziness, photophobia, blurred vision, abdominal pain, myalgia, weakness, difficulty breathing, fainting, mydriasis, and peripheral cyanosis occurred throughout the West Bank. Six hundred and sixty (70%) of the patients were school girls between the ages of 12 and 17 years. Clinical, epidemiologic, and toxicologie analyses indicated the illness was of psychogenic origin, induced by stress. The outbreak, which began at a girls' secondary school, may have been triggered by the odor of low concentrations of hydrogen sulfide gas near the school.