From being a relatively neglected fi eld, the study of de facto states has developed rapidly in recent years. As the break-up of the Soviet Union produced seven de facto states -four that still exist to this day (Abkhazia, Nagorno-Karabakh, South Ossetia and Transnistria) and three that are now defunct (Chechnya, the Donetsk People's Republic and the Lugansk People's Republic) -scholars from this region have contributed greatly to the development of this fi eld. Russian scholars have been particularly active, with Russia serving as the patron state of three of the extant entities (having reintegrated/absorbed the three defunct ones), as well as of the patron of Nagorno-Karabakh, Armenia. But Western scholars have also made a sizeable contribution, although often working in relative isolation from "local" research. Whereas local researchers excel in in-depth knowledge of the history and culture of the region, their Western colleagues add to the comparative and theoretical approaches. And just as Russian researchers naturally focus on the relations of the Eurasian de facto states with their Russian patron, their Western counterparts often analyse the policies of their own countries towards these entities. Thus, we argue, two separate "ecosystems" of research into Eurasian de facto states have gradually developed: a "local" one and a "Western" one, each with its own peculiarities. In this article, we survey the "Western" literature on de facto states, noting the various assessments of the possibilities for US and EU engagement with the Eurasian de facto states. The scholarly literature discussing Western engagement emerges as partly analytical, explaining what Western states are doing and not doing and why, and partly normative, off ering policy recommendations on how best to engage. Implicit in the concept of "engagement," however, is the understanding that engagement is preferable to "ignoring" or "sanctioning." According to this view, Western cooperation with de facto state authorities is inevitable.