The profile structure has been determined for bilayers of three highly polymerizable diacetylenic glutamate lipids (DGL), bis(docosa-10,12-diynyl) N-[6-(triethylammonio)hexanoyl]-L-glutamate bromide (DGL-1), N-[11-(trimethylammonino)undecanoyl]-L-glutamate bromide (DGL-2), and N-[4-(trimethylammonio)butoxybenzoyl]-L-glutamate bromide (DGL-3). Bilayers of each lipid are similar in structure, with lamellar profile and equatorial reflections that are consistent with a tilted lamellar phase with Mi packing. The structures are distinct from previously reported structures of diacetylenic glycerophosphocholines, since the acyl chains do not appear to be offset in the bilayer normal direction and are not as crystalline. Langmuir compression isotherms of DGL-1 and DGL-2 monolayers on water show no clear transitions, whereas those of DGL-3 have several transitions. All three lipids are readily polymerizable as Langmuir films. Model structures are proposed for the DGL bilayers which distinguish them from the previously reported diacetylenic glycerophosphocholine bilayer structures.