We verify the effects of sovereign rating revisions on the activity of European banks, in terms of their regulatory capital ratio, profitability, liquidity, and lending supply. First, we find that a sovereign downgrade has a significant impact, primarily on capital ratios and lending supply. In contrast, upgrades do not have a significant impact, indicating an asymmetric effect of sovereign rating changes. Second, we find that three transmission channels (assets channel, funding channel, and rating channel) explain a relevant part of the impact of a sovereign downgrade. Finally, we find strong evidence that the rating-based regulation affects all measures of the activity of domestic banks, causing negative externalities for financial institutions. Our results hold also controlling for sovereign risk, estimating a GMM system, and employing an instrumental variable approach. (C) 2017 Elsevier B.V. All rights reserved.