Research from a Fulbright Police Fellowship conducted in summer 2001 studying US attitudes and policies to inter- national law enforcement cooperation is presented. Differences between UK police and the multitude of US federal agencies in approaches to investigating transnational organised crime are identified, along with the implications for conducting evidence- gathering abroad and joint operations. No one approach is either right or wrong: the key to successful investigations lies in accommodating, rather than bemoaning, political and cultural differences in attitudes to law enforcement. This article alerts investigators to some of the issues they may encounter in transatlantic cooperation. Although researched and largely written prior to 11 September 2001, the aftermath of those events has not materially affected the conclusions drawn here. Positive attitudes to cooperation have been promoted, but some differences in approach have also been enhanced.