Abstract : This paper introduces Madeleine II, a new adaptive and portable multi-protoco- l communication library. Madeleine II has the ability to control multiple network protocols (BIP, SISCI, VIA) and multiple network adapters (Ethernet, Myrinet, SCI) within the same application session. Moreover, it includes advanced mechanisms to dynamically select the most appropriate transfer method for a given network protocol according to various parameters such as data size or responsiveness user requirements. We report on performance measurements obtained using BIP and SCI and we present preliminary results about our Nexus/Madeleine II and MPICH/Madeleine II ports.