Since 1979, FMC has conducted various studies to evaluate the effect of rainfall on residue and efficacy of EC (emulsified) and ULV (nonemulsified) permethrin formulations. Interest in this subject arose from the use of our pyrethroid insecticide, Pounce (permethrin), in reduced volume sprays with vegetable oils. Laboratory studies, using artificial rain, and field studies, using overhead irrigation and natural rainfall, have been performed with varied pests and crops. These include southern armyworm, Spodoptera eridamia on pinto beans, Heliothis spp. on cotton and soybean looper Pseudyplusia includens, on soybeans. The effects of rainfall on emulsified formulations applies in water and vegetable oil were compared to the effects of rainfall on non-emulsified formulations applied in oil. Laboratory studies indicate no significant difference (P=0.05) in southern armyworm mortality when treatments were followed by a 1" or 2" rain. This was true whether the rain followed the applications after it had dried or whether the product was applied to wet plants (dew simulation) and then received rain. Season long aerial cotton trials from five states indicate that under natural rainfall conditions, there was no significant differences in Heliothis spp. damaged squares or seed cotton yields between emulsified formulations and non-emulsified formulations applied in oil. In addition, there was no significant difference in soybean looper mortality when natural rain followed vegetable oil applications of emulsified and non-emulsified formulations to soybeans. Thus, we feel that an EC formulation of our pyrethroid, Pounce^® allows flexibility for use in UVL oil, high volume water and tank mix applications that are required in current dynamic agricultural production programs.