During the Period from 22th to November 26th, 1971, An Epidemiological Survey was performed on the Accident which was occurred by Leakage of Chloride Gases in A Chemical Industry, one of Wul San Industrial Areas. The obtained results were as follows; 1. The largest damage was observed at Yeo Cheon Dong, 5.38 Km2 in Area and 8,192 in the Residents. 2. By the age distribution of Yeo Cheon Dong, The largest damaged area resulting from chloride accident, the age group of between 10 and 39 was highly occupied with 55.2% Of all Yeo Cheon residents. 3. The number of patient was 436 totally, 198 in male and 238 in female. 4. By the age group distribution of the patient, in case of male, the largest group was under 20 age (96) and female, between 20 and 40 age group. 5. By the educational level of the patient, No-Education group was 116 (26.6%), and primary school, middle school and high school were respectively 168 (38.5%), 68 (15.6%) and 12 (2.8%). 6. By the occupational distribution of the patient, No-Occupation group was 49.7%, students and agriculture were respectively 14.4% and 8.1%. 7. By the complaints of the patient, most of all were for respiratory tract, those are coughing (56.9%), chest tightness (35.6%), sore throat (24.8%), and so forth. 8. By the injured domestic animal, the Dog was most highly injured with 46.2%.