This paper concerns the study of information derived from the melodic, temporal and intensity characteristics of the material to be recognized in a speech recognition system, in French. More precisely, it describes experiments we achieved at the suprasegmental levels with a system that outperform automatic correlation between prosodic labels and linguistic organization of a message to decode. Firstly an overview of the system is described along with the results of experiments carried out to determine which prosodic indexes are best-suited for syntactic and rhythmycal prediction.