The European Union countries have witnessed increasing importance of migration for years, while contribution of natural increase to population change has visibly diminished. This poses a great pressure on migration research. In particular, searching for migration determinants becomes more and more important. In the years 1986-1994, EU12 constituted a relatively stable group of countries, thus investigation of possible migration determinants for these countries could deliver promising results. Data published by Eurostat and data from national statistical institutes of individual countries, supplemented by estimates based on numerous theories and empirical evidence, constitute a basis for the analysis of migration determinants for NUTS 2 regions. Assuming that internal and international flows of migration are undertaken simultaneously, regression analysis is used to indentify the impact of carefully selected independent variables. The regression results show that economic variables, typical for migration studies, do not play an important role in determining migration, while general measures of the standard of living (number of cars per 1000 and household energy consumption), along with population density and long-term unemployment rate, explain net migrations at a satisfactory level. However, regressions run for selected countries allow for better explanation of net migration by variables considered. These results suggest that migration determinants vary between the EU12 countries and further research is needed, on factors affecting migration, in particular by referring to spatial and temporal integration of migration flows.