The Trinity River Basin was among the first 20 hydrologic systems under full inplementation of the National Water Quality Assessment (NAWQA) Program. Planning and analysis of existing information began in 1991. Intensive water-quality data collection began in 1993. As a part of the NAWQA Program, pesticide samples were taken from surface water, ground water, streambed sediment, and aquatic-organism tissue in the Rush Creek watershed in Arlington, Texas, during 1993?94.