This article uses a survey of three French industrial establishments to examine the persistent difficulties of unionists to make issues of work organization a basis for collective action – especially when these issues result from lean production. The authors first revisit the ways in which lean management was introduced into each of these factories and the unionist critiques they occasioned, largely concentrated on dissent against the intensification of work and hierarchical pressure. The article then illustrates the ambivalence of surveyed unionists confronted with these reorganizations of work and the resulting fragility of worker mobilization, notably due to divisions generated both between unionists and among workers.