The effect of dichloro-diphenyl-trichloroethane on the soil flora was studied in soils and in pure cultures. No harmful effect was noted in soil by applying as much as 2% on the soluble salts on the accumulation of nitrate, ammonia, total population or on the nodulation of legumes. Growth of 11 strains of the legume bacteria, of 10 other spp. of bacteria, of 12 fungal spp., of 6 algal spp. and of 3 spp. of actinomycetes, all in pure cultures in test tubes, appeared normal even though excessive amts. of D.D.T. were spread on the surface of the medium.