A new class of ionic self-complementary oligopeptides is described, two members of which have been designated RAD16 and EAK16. These oligopeptides consist of regular repeats of alternating ionic hydrophilic and hydrophobic amino acids and associate to form stable beta-sheet structures in water. The addition of buffers containing millimolar amounts of monovalent salts or the transfer of a peptide solution into physiological solutions results in the spontaneous assembly of the oligopeptides into a stable, macroscopic membranous matrix. The matrix is composed of ordered filaments which form porous enclosures. A variety of mammalian cell types are able to attach to both RAD16 and EAK16 membranous matrices. These matrices provide a novel experimental system for analysing mechanisms of in vitro cell attachment and may have applications in in vivo studies of tissue regeneration, tissue transplantation and would healing.