Adsorption/desorption studies are conducted to understand the mobility of agrochemicals in soil and estimate the probability of their transport and distribution into various other compartments of our biosphere. The chapter discusses the batch equilibrium method for determination of sorption coefficients of agrochemicals in soil using a tiered approach. The tiers included a preliminary study to determine the optimum soil-solution ratio, to ascertain the proper equilibration time, and to quantify the amount of test substance adsorbed to soil at equilibrium. In the second tier, the distribution coefficient for adsorption Kd and the organic carbon-normalized distribution coefficient for adsorption Koc are determined in five different soil types using a single concentration of the test substance. In the Tier 3 main study, the Freundlich adsorption isotherms of the test substance are determined to study the influence of concentration of the test substance on the extent of adsorption to these soils. The Freundlich desorption isotherms are also determined in the main test in order to understand the desorption kinetics of the test substance from soil. Alternative methods for the estimation of sorption coefficients, such as those based on HPLC analysis and regression analysis of molecular connectivity indices, are also discussed in this chapter.