It has been estimated that 375,000 tons of pesticides are used for agriculture annually in the Midwest area of the United States, where approximately 65% of this total is used for production of corn and soybean crops (Clark et al., 1999). Within the Mississippi River Basin, greater than 100,000 tons of herbicides are used annually (Clark et al., 1999). Triazine herbicides (e.g. atrazine) and synthetic pyrethroids insecticides (e.g. λ−cyhalothrin) are two classes of pesticides currently used in this agricultural area. These two types of pesticides are very dissimilar, due to their differences in structural and physical properties. A major difference between these pesticides is polarity, where triazines are relatively more polar than pyrethroids.With demand for more rapid extractions and multiresidue pesticide analyses, analytical methods for environmental matrices, such as soil and plants, have been developed using new technologies (Kahn, 1995; Sánchez-Brunete et al., 1998). For example, traditional extraction methods, such as soxhlet and sonication, are being replaced with solid-phase extraction (SPE), solid-phase microextraction (SPME) and supercritical fluid extraction (SFE) techniques because they are less time consuming and require lower volumes of organic solvents (Hengel et al., 1997;Miege and Dugay, 1998;Camel, 1998). In some cases, newer analytical equipment is not available, therefore older methods using traditional equipment must be reevaluated.The following study presents the development of a rapid and sensitive gas chromatographic method using sonication for extraction of atrazine and λ− cyhalothrin in sediment and aquatic macrophytes. This method requires lower solvent volumes and reduced sample weights relative to the traditional EPA sonication method.In addition to method development, a storage stability test was performed to determine acceptable storage times for natural water samples containing pesticide residues. Natural water samples were fortified with atrazine, λ-cyhalothrin, and metolachlor, a chloroacetamide herbicide. These three pesticides represent three of the major classes of pesticides used extensively in row crop production in the area of the lower Mississippi River Basin known as the Mississippi Delta.