It is possible for Ukraine to use Ukrainian Rubles instead of Ukrainian Hryvnias, but it is highly unlikely. Ukraine has not issued its own currency since 1996, when the Hryvnia was adopted as the national currency. Any attempts to reintroduce the Ruble could be complicated by the fact that Russia is the primary issuer of Rubles and the two countries have had an historically hostile relationship. Moreover, the large amount of Hryvnia already in circulation would need to be replaced by Rubles. Therefore, until conditions between Ukraine and Russia change, it is unlikely that Ukraine will switch to the Ruble.