Being an emerging field of "omics" research, metabonomics has been increasingly used in toxicological studies mostly because this technology has the ability to provide more detailed information to elucidate mechanism of toxicity. As an interdisciplinary field of science, metabonomics combines analytical chemistry, bioinformatics, statistics, and biochemistry. When applied to toxicology, metabonomics also includes aspects of patho-biochemistry, systems biology, and molecular diagnostics. During a toxicological study, the metabolic changes over time and dose after chemical treatment can be monitored. Therefore, the most important use of this emerging technology is the identification of signatures of toxicity-patterns of metabolic changes predictive of a hazard manifestation. This chapter summarizes the current state of metabonomics technology and its applications in various areas of toxicological studies.