This is a general protocol for the isolation and maintenance of primary MPM cultures as a tool for the identification of Tumor Initiating Cells and early progenitor-targeting drugs (Cioce et al., 2010). Primary cultures can be propagated efficiently for 8-12 weeks and xenotransplanted in NOD/SCID mice while retaining the histofeatures of the originating tumor (Canino et al., 2012). The protocol is suitable for both MPM solid specimens and pleural effusion. For increased clarity, initially two separate sections addressing the isolation of MPM cells from solid tumors and pleural effusions are here provided.