This chapter contains 47 well illustrated diagrams. Chapter starts with description of quantitative evaluation of vestibular functions followed by assessment of auditory function and ends with description of cochlear and brain stem implants. It covers comprehensively electronystagmography, electrooculography, optokinetic testing and calorie test. Auditory assessment is described in detail from electrophysiological tests to auditory brain stem response. Adequate illustrations of clinical conditions related to defects of auditory pathway are included in this chapter. Clinical conditions are summarised in tables. Different cochlear and brain stem implants are described with pictures. Indications, method of post operative assessment of implants and complications of implants are described in detail. Good number of references are given for implants and assessment tests separately for further reading.