The first part of this paper surveys common techniques for representing speech in voice response systems. Two major classes of techniques--waveform coding and parametric coding--and their variants are presented. The encoding, decoding, and synthesis techniques as well as the advantages and disadvantages of each method are discussed. The second part surveys two types of voice response systems: systems with limited vocabulary and systems with unlimited vocabulary. Some examples of the latter type of system are described and discussed. Finally, some applications of voice response systems are discussed.