After the elimination of last bison in the wild between 1919-1926, successful re-introduction of this species in Ukraine started in 1965. Animals originated from various breeding centres in Russia, Byelorussia, Lithuania, and Crimean Peninsula, Introduction took place in 4 sites in the Carpathians, and in 7 lowland parts of the country. After an initial growth of the population, a decline in bison numbers is observed since the mid-nineties. At present, there are 489 bison in Ukraine, in 11 free - ranging herds of size varying between 3-148 individuals. At least two of them are at critical situation. Mortality results mostly from poaching, over-hunting and some endemic diseases. Unknown remain also genetic aspects like the level of inbreeding - potentially limiting reproductive success, or contributing to lower survival rate. Among the most important aspects is potential crossbreeding of animals belonging to pure lowland Bialowieza line, with those of mixed lowland - Caucasian descent. That may become a major threat for a significant part of original gene pool of European bison. Sound management of the free-ranging bison is at the moment possible only on the basis of detailed examination of existing bison records, pedigree books etc. The analysis of long-term records on the origin of a herd, sex composition, breeding history etc. is necessary to create the data base necessary for further exchange of individuals, designing supplementing procedure for threatened herds, and re-introductions connected with the program of European bison re-establishment in the Carpathians and Ukraine.