Fines are one of the Commission’s main tools for the enforcement of Articles 101 and 102 TFEU. While the Commission’s fining policy has evolved over time towards a higher degree of transparency and predictability, as illustrated by the publication of the 1998 and 2006 Guidelines for the setting of fines,1 certain aspects of the calculation of fines nonetheless remain controversial. This article discusses selected issues raised by recent Commission or Court decisions in respect of cartel fines, in particular as regards (i) the addressees of cartel fines decisions in case of vertically integrated undertakings, (ii) the inclusion of captive sales in the basic value of sales for the calculation of fines on cartel participants, (iii) the EU Courts’ full jurisdiction with respect to cartel fines decisions, and (iv) the policy issues raised by this jurisdiction, in particular regarding the proportionality principle.