The study is introducing an overview of main trends in the approach to the questions of intellectual migration in framework of UNESCO project ''Problems of brain drain in Europe''. One of the most important problems, affecting the development of countries of Middle and Eastern Europe, which are going through process of transformation to the market economy, is problem of intellectual migration. The first meeting of working group of BD was realized on the base of invitation of Calouste Gulbenkian Foundation during November 26 - 28, 1990 in Lisbon and led directly to the creation of UNESCO project ''Brain Drain Issues in Europe'' and its coordinating group (Task Force). From 1990 the problem of mass intellectual migration is dealt with in post-communist countries on actual level, but very rarely on level of expert articles and scientific studies. Basically, it is necessary to distinguish ethnic migration from work migration, when intellectual migration can have ethnic dimension (ethnic discrimination of scientist), or labor dimension (an opportunity to work in better conditions). Brain Drain has two main aspects - positive and negative. Because science of today is without boundaries (Hryniewicz 1992), scientific discoveries because sooner or later property of all humankind. In this sense the phenomenon of BD is highly positive. Negative consequences are noticeable in countries, from which scientists are departing and are very serious, namely from long term perspective. BD for one country (or for science in general) means profit - Brain Gain, but for other country it a long term loss - Brain Drain. Polish study is analyzing Brain Flight or simply migration, not Brain Drain, which is enabling to accept so called push - pull factors. It is a set of inverse factors, which can have social nature (social status of scientist), economic (financial evaluation of scientist), psychological (conditions for scientific work) or others. These factors in home country imply a noticeable ''mechanism of pressure'' (push), but in receiving country abroad function as positive ''attracting mechanism'' (pull). Brain Drain is not only movement of intellectual capital (Teplan 1991), that is personal BD, but also ''draining of results''- escape of knowledge and information. From the aspect of mobility we can summarily discern: 1. internal mobility of scientists - physical movement among sectors of one country, so called internal BD, 2. internal mobility of ideas - communication network among sectors and regions of one country, 3. external mobility of scientists - movement with the intention to visit other countries in context of scientific exchange, scholarships, conferences, and so on, 4. external mobility of ideas - international communication network, 5. external migration of scientists - reasonably stable flow of scientists into other countries - authentic, so called external BD (Murris 1993). We talk about BD only in the case, when an emigrant is working in his (her) field, or proceeding in enhancement of qualification in new (better) conditions. In case when an emigrant is working in other field and gradually is loosing qualification, some authors are talking about Brain Waste. Generally valid factors of BD: insecurity and instability of socio-economic development of countries of Middle and Eastern Europe during the transition to market economy, decrease in long term capital investments into the sphere of research and development, low ability of research centers and individual scientists to withstood competition, lack of qualified management in science in environment of free market. Influence of mentioned push - pull factors imply following transfer of intellectual potential (personal and informational) from less developed countries into the more developed and is enabling real function of so called conception of ''center - periphery'', oriented on identification of direction of transfer of intellectual resources. Stated concept is not universally applicable, but it is expression of dominant direction of BD. Solving of methodological questions of BD research is an important step in aim for coordination, comparability precision and representativity of research activities. In the actual stage of BD research, the approaches and methods are applied on level of national studies and are offering only an overview of realized and potentially possible processes. In reason to solve problem of intellectual migration not only on level of facts and quantitative analysis, but create also suitable theoretical and conceptual hinterground, Trestieni (1991) is suggesting several possible initial approaches. Phenomenon of BD is possible research from the aspects of theory of justice; where basic direction is research of degree of satisfaction (or dissatisfaction). This approach is giving the possibility to answer if that what scientist is receiving from the society for his (her) work (and life), is justful or not. Second approach is coming out of theory of social comparison and its findings are answering the question of scientists' satisfaction when compared with the other people. For the research of BD is interesting also so called competition model (K. Willis, N. Ritchey), which accentuate significance of differences of average salaries of various groups of population. More complex, in the aspect of compared indicators, is so called gravitational model, which is enabling to observe and compare differences among territorial units (zones). Theory of quality of life (D. Sandu) is leading researched phenomena towards such factors as availability of certain products (goods) necessities and luxuries, existence of adequate network of services, interpersonal relations, differences in the hierarchy of life needs - primary (food, place to stay) and operative (selfrealization). In many national studies a potential BD is observed, which is - according to stated data - percentually extraordinarily high. Numerous suggestions exist to create a typology of scientists in general and emigrant scientists with the minimum of proven difference in at least several levels. Phenomenon of BD is interesting also from the aspect of activities of emigrants in receiving country. Occasionally, in frame of elaborated national analyses, there are studies focused on one concrete area of scientific research (Trestieni 1993 BD in physics). With the exception of stated possibilities and suggestions of methodological procedures, part of research of BD phenomena is also an analysis of main directions (flows) of BD. In reason to secure the real possibilities to coordinate the work on UNESCO project, the concrete procedures were suggested (Vyrost 1991), which, unfortunately, were not kept by participating countries. These procedures, in line with the planned analyses, divided the research space into three main phases: The first phase of analysis of socio-economic, political and cultural conditions of country; the second phase of global quantitative analysis of scientific and development base; and the third phase of research of latent BD in concrete conditions of basic research (sociologic probe) with the aim to state a diagnosis of objective and subjective factors of BD. Dynamics of development of BD was intended to be observed during the years of 1988 - 1993 with the specific focus on selected scientific fields - physics, biology, computer sciences and economy.
