This article analyses different standard measures of legislative turnover. Two main concerns are discussed: (1) the very definition of turnover: incoming MPs versus first-term MPs; and (2) the level of analysis: the whole chamber versus political groups. To illustrate this discussion, turnover in the French lower chamber, the Assemblée Nationale, is studied. It is shown that the choice of a particular measure is not trivial since empirical results are affected by the definition adopted. If the distinction between incoming and first-term MPs does not greatly modify results, the choice of the level of analysis leads to contradictory results. It is shown that the very logic of electoral contests leads to renewal mostly among those who lost previous elections, while incumbent majorities that lose elections hardly experience renewal. As both these phenomena coexist for every single election, aggregate measures of turnover do not account for these contradictory tendencies and tend to concentrate on alternation rather than turnover.