Through analysis of adult-deaf child and adult-SLI child interaction, and after the presentation of the theoretical frame and aims of Interactive Developmental Intonology, we try to better understand the importance of prosody in early language acquisition. Our research focuses on suprasegmental development - rhythmical and melodic organization in the interaction -, and its effects on conversational and linguistic competences of handicapped children. Which are the conditions for sounds to become a canonical sentence? How a prelinguistic utterance, without words, can nevertheless have a linguistic modality?