Hydrolysis tests are conducted on an agrochemical compound under a tiered approach to gather information on the nature of its abiotic hydrolytic degradation process under environmental conditions. Test solutions are prepared in sterile aqueous solutions buffered at pH 4, 7, and 9 and incubated in the dark at a constant temperature. The hydrolysis test is normally carried out for a period of 30 days, but the test may be terminated earlier when 90% hydrolysis is achieved. Test samples are analyzed at a minimum of 6 specific intervals, and the concentrations of the test compound and its transformation products are quantified. The hydrolysis rate constants and half-lives of the test compound are determined from these tests. The degradation products are identified to discover the hydrolytic pathways of the test chemical. Hydrolytic pathways of various groups of agrochemicals are also presented in this chapter.