The author first recalls a few notions which may be end useful in order to enlighten the debate concerning the «new ministries» in the Church: the Baptismal coresponsibility of all and the ministerial collaboration of a few; the ministries (ministeria) on the one hand, and the charges (munera) and functions (officia) on the other; associative communities and hierarchical communities. It is in the context of those hierarchal communities that one may consider the possibility of «new ministries ». Taking into consideration the institutional logic specific to the hierarchical communities, the author expresses four conditions required for creating lay ministries. The study does not pretend to be exhaustive; it only proposes a few rules of canonical grammar at the service of ecclesial life.