The terrorist attacks that swept Europe in 2014–2016 underscored the vital importance of US–EU law enforcement cooperation. Nearly all the attacks had an international component and occurred because of dramatic failures of police and intelligence services to share information on a timely basis. The United States has gradually built up its cooperation with Europol, the EU’s police agency, because of Europol’s growing contributions in the joint struggle against serious crime and terrorism. US–EU Agreements, such as those dealing with the exchange of passenger name records, data privacy protections for the transfer of law enforcement data and US access to records of financial transactions held by SWIFT, have made a substantial contribution to enhancing transatlantic and even global security. The US and the EU now need to negotiate an agreement on their reciprocal access to electronic evidence to assist law enforcement authorities to respond quickly to serious crime and terrorist acts.