The Mississippi River and its tributaries serve as a drainage system for surface water for a large part of the United States. A recent report attributed fish kills which occurred between October 1963 and February 1964 in the lower Mississippi River to minute quantities of endrin in the fish. This same report states that dieldrin and endrin are both present in the drinking water of the city of New Orleans and that dieldrin, endrin, heptachlor, DDT, and DDE have all been found in shrimp from the Gulf of Mexico. The storage of chlorinated hydrocarbon pesticides in the fat of people without occupational exposure is well known. In view of the above report the following study was conducted to determine the concentration of these materials in the fat of people in New Orleans.