Abstract: At approximately 9:30 a.m. on May 27, 1993, employees in the northwest corner of the facility started smelling a bug spray odor. Wilson Pest Control was on site spraying the exterior of the building with the insecticide, Diazinon 4E. The exterminator had begun spraying at about 9:15 a.m. The odor eventually spread throughout the Reservations floor. Employees became nauseated and light headed and asked permission to go outside for fresh air. The fire department was contacted to treat personnel. After the facility was totally evacuated and all personnel were in the parking area, others began to get sick with a variety of symptoms. EMS units were called to assist. Employees were told to go to the doctor if necessary and many were transported by ambulance to the hospital. Sixty-four employees were treated at different medical facilities in the area. Two employees were hospitalized--Employee # 11 with an irregular heart beat and Employee #20 for unstable respiration.