This paper proposes a modified speech coder, namely the MPEG-4 harmonic vector excitation coder (HVXC), for adaptation of the relative speech rate. Applied to the conversion of voice characteristics it can be used to partially restore the speaking style of a specific speaker which can get lost during the process of a frame-by-frame voice conversion. Furthermore, a method for estimation of the relative speech rate between two different speakers will be given.The results show that the speech rate can be adapted by the proposed system with almost no quality decrease of the synthesized speech.