This paper considers applications of automatic speech recognition and speaker verification techniques in developing efficient Voice Messaging Systems for Integrated Services Digital Network (ISDN) based communication systems. The prototype demonstrator presented was developed in the framework of cooperative project which involves two research institutes: the Signal Processing Laboratory (LTS) of the Swiss Federal Institute of Technology Lausanne (EPFL) and the Dalle Molle Institute for Perceptive Artificial Intelligence, Martigny (IDIAP), and three industrial partners: the Advanced Communication Services (aComm), SunMicrosystems (Switzerland) and the Swiss Telecom PTT [1]. The project is supported by the Commission for Technology and Innovation (CTI). The goal of the project is to make available basic technologies for automatic speech recognition and speaker verification on multi-processor SunSPARC workstation and SwissNet (ISDN) platform to industrial partners. The developed algorithms provide the necessary tools to design and implement workstation oriented voice messaging demonstrators for telephone quality Swiss French. The speech recognition algorithms are based on speaker independent exible vocabulary technology and speaker verification is performed by a number of techniques executed in parallel, and combined for optimal decision. The recognition results obtained validate the exible vocabulary approach which offers the potential to build word models for any application vocabulary from a single set of phonetic sub-word units trained with the Swiss French Polyphone database.