The use of Pesticide Leaching Models (PLM) for risk assessment may be an efficient and attractive way of assessing solutions to some agricultural and environmental problems. Many countries of the European Union and the USA have been using PLM for risk assessment already for a few decades. This chapter has the aim to present a successful application of two PLM (i.e. MACRO and PEARL) in a Brazilian very intensive agricultural area to simulate moisture profiles and the leaching of a water flow tracer (i.e. bromide) and the pesticides cyproconazole and thiamethoxam. Also attempts to summarize the available knowledge about the processes governing pesticide behavior in soil, types and classifications of PLM, the use of PLM for risk assessment at European Union, a theoretical description of PEARL and MACRO models and their testing in a Brazilian agricultural field scenario.
