Although regulatory agencies require adsorption and soil mobility data prior to registering pesticides, such data are not necessarily adequate to accurately predict the environmental fate or mobility of any particular chemical. The unexpected detection of hydrophobic pesticides in remote ecosystems and ground waters, compounds deemed immobile based on their partition coeffi cients, is indicative of an incomplete understanding of pesticide adsorption and desorption processes in natural environments (McCall et al. 1980; Corsolini et al. 2002; Montone et al. 2005) . One key element needed to fill this knowledge gap, in addition to continued basic research, is to comprehensively synthesize existing research findings pertinent to the adsorption and desorption of pesticides. Therefore, we have analyzed an extensive number of peer-reviewed journal articles, and herewith present a critical examination of the environmental presence, adsorption, and desorption of chlorpyrifos (CPF), one of the most widely used organophosphorus pesticides worldwide. This review complements past reviews that have addressed the environmental fate and ecotoxicology of CPF (Racke 1993; Barron and Woodburn 1995; Giesy et al. 1999), and the general process of soil adsorption for multiple pesticides (Delle Site 2001 ; Wauchope et al. 2002 ) . We fi rst review the environmental presence of CPF and then address CPF adsorption data for a range of solid matrices, including soils, sediments, organic matter, and minerals. Our review was performed using the framework of the common methods employed to quantify pesticide adsorption: batch equilibrium, chromatography, and use of ancillary pesticide characteristics such as water solubility, the octanol–water partition coefficient, and topological structure. Thereafter, we address peer-reviewed data that documents CPF desorption, a key process that affects the long-term fate and impact of CPF in the environment, but has heretofore been inadequately addressed. We conclude the review by providing key recommendations for future research.