This thesis focuser on the evolution of Bulgarian agricultural cooperative movement in the context of the capitalist market economy and of the socialist one. We examine the challenges agricultural cooperatives have been facing, the strategies they have to adopt to overcome them and the consequences those strategies have on the performers and activities of an agro-economy and on the sociétariat of their members.Our main purpose is to sort out problems related to the development of cooperatives (1) as associations which should satisfy the needs of their members and those of their social background and (2) as businesses which should be run according to the rules of the market economy, be it the capitalist or socialist one. Such a purpose inevitably raises questions about the different strategies to develop cooperatives, about their impact on the very nature of the cooperative movement itself and on the role they play in the socio-economic transformation of the society.The originality of our study lies in the fact that ours is the first attempt to explore, in a historical, analytical and global way, how the Bulgarian agricultural cooperative movement has evolved. There is no other contemporary study [published in Bulgarian or in French) on the subject and our purpose is to fill this gap. The analysis of different socio-economic circumstances helps us to understand how cooperatives were born and have been transformed from one type into another, and also what strategies they had to adopt to defend their interests.Our study traces back the origins of the fast cooperative movement in the world, that has influenced the development of all cooperatives in the Balkan Peninsula and in particular those in Bulgaria. The pre-cooperative forms anchored in the Slav tradition as mutual aid and the more modern ones adopted after the liberation from the Turks, contributed to setting up the organizational forms of cooperatives which are still running today.Methodology . After having reviewed the various theories of cooperation, we built our ideal model on the analyses done by Claude Vienney and Guy Desforges. This model lets us study the cooperative movement as a process of performers assertion, as activities and rules of operation in a capitalist economy (marked by competition), or a socialist one (marked by competitiveness). Two research techniques were used: the documentary technique and the technique of the structured interview.We came to the conclusion that a socialist economy causes a lack of balance in supply and demand. The same event in the capitalist economy, would be the essential element to intensify competition and becomes the driving force of this type of economy. In the socialist economy however, competition does not exist, it is replaced by competitiveness. When an economy crumbles due to central planning, the competition is of a rather quantitative character. It means that salesmen and customers, locally and internationally, get the same ability to bargain. Any lack of balance between supply and demand are regulated here by the State Administration. The latter says that competition exists in a socialist economy, but it is less well expressed (i.e., it is insignificant).We observe a hierarchical division between the basic forms of cooperatives, namely the regional cooperatives and the unions of agricultural cooperatives. This division reveals the existence of a close connection between the size of a cooperative and its importance toward the sociétariat the credits and the income of the movement. We realize that larger cooperatives, having a higher position in the hierarchical division of activities, have more opportunities and lead the movement in the direction which suits best their interests.In short , the adaptation of the agricultural cooperatives to the rules of the existing economy, either capitalist or socialist, specifies them as institutions and this distinguishes them from all other types of companies.