**Abstract**

In this chapter, recent data on the clinical application of the frequency following response (FFR) in different age groups will be presented. The chapter begins with the importance of using speech sounds in electrophysiological assessments. Then the FFR methodology is presented, giving normative data and the expected responses in different age groups: infants and young children, children and adolescents, and adults and the elderly. Finally, the unique responses of each age group are presented in order to show how this new technology can be an extremely useful tool for diagnosing hearing dysfunction.

**Keywords:** electrophysiology, frequency following response, speech perception, hearing, auditory evoked potential
