Confined rotational crop study of an agrochemical is conducted to apply rotational crop restriction, define its terminal residue in RAC samples, and develop residue definition for field crop trials. The confined rotational crop study is essentially a compendium of multiple plant metabolism studies on several crop species grown in treated soil. The test substance is radiolabeled with 14C to facilitate quantification of residue, identification of metabolites, and elucidation of metabolic pathways. The test plants are selected from three different crop groups: leafy vegetables, root crops, and small grains. The agrochemical is applied to bare soil in test plots at 1 × maximum seasonal use rate as recommended in the use label of the agrochemical product. The crops are planted in the test plots at three different intervals to cover all possible scenarios of crop rotation. The RAC samples are harvested at the appropriate growth stages, and samples containing significant residue are extracted and analyzed to identify/characterize major residue components. Metabolites with toxicological concern are included in the residue definition for risk assessment and tolerance enforcement in the field rotational crops studies. The chapter also describes conduct of a confined rotational crop study and discusses metabolic pathways of a selected group of agrochemicals in confined rotational crops.