The structures of the French dairy industry has entered a phase of rapid reorganization in seven years, 1 705 dairy units (out of 6 000) have « disappeared ». After appreciating the importance of this concentration, the authors have tried to analyse the technical' and economic factors which influence the growth of dairy firms. The essential phenomenon is the growth of a small number of big firms. This' growth seems to take two main directions : — control of the market of new products — control of a high-consuming geographical area.