This article aims at identifying European agencies' rulemaking powers, mapping the procedures through which such powers are exercised and assessing the existing procedural arrangements. The first section analyses the main forms of European agencies' rulemaking. It shows, on the one hand, that not all European agencies are actually engaged in the adoption of administrative rules, on the other hand, that European agencies carrying out rulemaking activities tend to converge on two specific forms of rulemaking, namely participation in the adoption of binding implementing rules and regulation by soft law. The second section, devoted to mapping the procedures through which rulemaking powers are exercised, argues that the two main types of European agencies' rulemaking cannot be said to be subject to a really common procedural framework. In both cases, the emerging procedural rules implement the same principles of transparency and participation and rely on the same consultation mechanism, sometimes complemented by regulatory impact assessment. Yet, proceduralisation has an uneven development: while the establishment of a procedural discipline is quite common with reference to participation in the adoption of binding implementing rules, regulation by soft law remains largely under-proceduralised. The last section proposes an assessment of the European agencies' rulemaking procedures. Two main shortcomings are identified: the asymmetry between the tendency to proceduralise the adoption of binding implementing rules and the parallel tendency to keep informal the process of adoption of soft law measures; and the too rudimental development of consultation.