Abstract : This paper analyses the intuitionistic provability in classical logic and in linear logic. It proposes new labelled sequent calculi to analyse if a classical proof can be used to deal with intuitionistic provability of a formula. In the case of linear logic, labelled proof nets are defined for such a purpose and a characterization of provability , based on proof nets, is given. Moreover, the corresponding method is complete with respect to intuitionistic provability.