This article attempts to pin down the notion of "register" (niveau de langue) : its origin, the terms related to it and the sociolinguistic framework which attempts to correlate linguistic facts with extra-linguistic variables. It then proceeds to indicate the difficulties raised by this notion : 1) its failure to distinguish social and stylistic features other than with reference to stereotypes, 2) the impossibility of fixing the number of points and of hierarchising them along a linguistic scale, 3) seeing each point on the scale as a homogeneous entity and ignoring the inherent variability of language and the possibility of differences of meaning. The conclusion is that even as a pedagogic device this notion is a harmful one, given the oversimplified notion of language which it implies.