This paper presents an original technique for solving the phonetic segmentation problem. It is based on the use of a speech synthesizer for the alignment of a text on its corresponding speech signal. A high-quality digital speech synthesizer is used to create a synthetic reference speech pattern used in the alignment process. This approach has the great advantage on other approaches that no training stage (hence no labeled database) is needed. The system has been mainly evaluated on French read utterances. Other evaluations have been made on other languages like English, German, Romanian and Spanish. Following these experiments, the system seems to be a powerful tool for the automatic constitution of large phonetically and prosodically labeled speech databases. The availability of such corpora will be a key point for the development of improved speech synthesis and recognition systems.