Seven fields (Ulysses silt loam, Kansas; Knox silt loam, Kansas; muck, Ohio; sandy loam, Ohio; sandy loam, Miami silt loam, and muck, Wisconsin) were treated in 1954 with DDT (10,100 and 1,000 lb./6" acre), aldrin (2, 20 and 200 lb./6" acre) and lindane (1, 10, and 100 lb/6" acre). DDT was found to be the most persistent of the three. Lindane had the fastest dissipation rate. Soils treated with aldrin at 2 lb/6" acre in 1954 contained no aldrin in the fall of 1958, but 0.03 to 0.19 p.p.m. of dieldrin was recovered. No lindane was detected in soils 4 ½ Years after treatment at 1 lb/6" acre. All three insecticides disappeared most rapidly in the Kansas experimental soils. Two major factors affecting the persistence of an insecticide in soils appear to be the amount of organic matter within a particular soil type and the climatic conditions of the area.