Electricity systems have a central role to play in the transition towards a low carbon economy and the integration of renewable energy sources in the European Union (EU). However, European electricity networks face a diverse set of existing and new risks that can hamper the energy security of the member countries. This paper qualitatively and quantitatively assesses these risks given the changing operating framework characterized by market liberalization and network interconnectedness. Within this context, the paper primarily focuses on the risks from exceptional events and threats to European electricity systems. A simple ex ante risk assessment matrix is proposed to gauge the network risks and take preventative measures. This assessment mechanism can complement the existing ex post reliability and quality of supply performance standards and indicators used by policymakers and practitioners. The analysis presented in this paper suggests that economic risks pose the most serious and challenging threat to the evolving European electricity system. 2013 Elsevier B.V.