This article draws attention to the Commission's use of soft law within the EU state aid regime and discusses how the application of informal policy instruments by the Commission has evolved since the early 1990s. It argues that developments over the past decade have led to a 'hardening' of the regulatory approach applied within the state aid regime, an evolution which seems to run against a more general EU trend towards soft law and the introduction of 'softer' forms of governance. Yet this policy development should not be read simply as a trend from hard law to soft law. Rather, the reconfiguration of policy instruments used in the state aid regime reflects the challenges facing, and the distinctive characteristics defining, this policy area. The article thus begins by introducing and defining soft law. It then provides an overview of the distinctive characteristics of the EU's state aid regime and of Commission rule-making on state aid matters. The article concludes by pointing to two legal 'events' that have altered the Commission's soft law approach and by analysing and drawing out some of the implications of these developments.