There is no satisfactory solution to the problem of personal and place names in a work in English on east European history. I have tried to balance the conflicting claims of consistency and comprehensibility for readers unacquainted with east European languages. With regard to personal names, where an adequate English equivalent exists I have used it for the first names of ruling princes and members of royal families. Otherwise I use the Polish, German, Ukrainian, or Russian form where appropriate. I have used transliterations from Ukrainian rather than the Polish form for the names of Cossack leaders, thus Khmelnytskyi, not Chmielnicki; Vyhovskyi, not Wychowski. With regard to place names, wherever possible I have used the modern English equivalent, the seventeenth-century English equivalent for place names no longer used (for example Samogitia for Żmudż) or the form most familiar to English-speaking readers. On occasion this means preferring a Russian to a Polish, Belorussian, or Ukrainian form: thus Mogilev, not Mahiliou; Chernigov, not Chernihiv; and Brest (Litovsk) for Brześć Litewski. With regard to cities and provinces whose cultural and ethnic composition has changed radically I have preferred as far as possible the form used by the dominant linguistic group in the seventeenth century. Thus, for places in Prussia and Silesia German has been preferred: Danzig, not Gdańsk; Thorn, not Toruń; Breslau, not Wroclaw.