This chapter focuses on the development and application of genomics to tiered testing. It attempts to capture the potential utility of genomics for enhancing tiered testing, including how genomics may be used to support streamlining of the present chemical testing process. The chapter addresses the immediate and longer term goals for genomic tools in tiered testing, including identifying the associated research needs, and addresses the likely impacts (and longer term benefits) on animal testing, and the associated financial costs. Finally, the chapter presents a series of regulatory challenges and recommendations for the development and implementation of genomics into tiered testing. However, to appreciate how genomics might be developed for, and applied to, tiered testing requires an appreciation for how tiered testing works in the risk assessment of chemicals. The initial part of this chapter, therefore, sets out the present (and evolving) framework for this.