The present chapter gives an overview of the chemiluminescent and bioluminescent reactions' applications in the field of biosensors. Both light emitting reactions are, in a first part, thoroughly described together with biosensors and immunosensors basic concepts.

Then, analytical applications of these luminescent reactions are presented and commented. Particular attention is given to the experimental systems used (batch, flow, reaction triggering system) and the performances obtained (dynamic range, limit of detection). All over the chapter, electrochemiluminescence (as part of the chemiluminescent system) will be presented as a separated light emitting system since it has generated numbers of analytical applications and innovative experimental set ups.