This paper aims at : 1. Explaining why data are essential in order to study phonological phenomena at the postlexical level, be they segmental such as liaison and “enchaînement”, or suprasegmental such as accentuation or intonation. This results mainly from the fact that the analysis of these phenomena must take into account various types of information that may enter in conflict ; 2. Showing how data are designed in this field of research. In doing so, we will insist on the form and the content of the data used ; 3. Arguing that data constructed by the linguist and recorded in specific contexts as well as oral corpora are complementary in developing a linguistic analysis, both having their own advantages and limitations.