For several years, small shops in Spain and in other European countries have found themselves facing up to a situation of increasing convergence with the inrush of new commercial ways which are more vertical and horizontally integrated and better prepared to compete in price and variety. Faced with this fact, the trade associations (central offices of purchasing) offer themselves as an alternative designed to reduce distances on these two questions and at the same time providing certain services to help the small trader to manage his business more efficiently and effectively. In this article before you, this recent evolution and the supply trend by the small shops through the trade associations (central offices of purchasing) in Spain are analysed. Then, through an empirical study, it is tried to establish the answers of the small shops to a suggested relationship of points in favour and against which grouping together in a trade association (central office of purchasing) would suppose. With regards to this question, it is analysed in a particular way, to what extent we can relate the size of the commercial company with the degree of agreement with the trade associations (central office of purchasing).