Neutron reflectivity and II-A isotherm measurements of Langmuir films of polyether dendrimers based on 3,5-dihydroxybenzyl alcohol have elucidated the structure of these interesting molecules at the air-water interface. The neutron reflectivity measurements indicated a collapse of the fourth-generation monodendron, [G-4]-OH, to a bilayer structure. The molecules in the layer next to the water interface were ellipsoidal in structure due to compression and contained a volume fraction of about 25% of the substrate water. The molecules in the layer next to air were spherical with a diameter of 21 Angstrom and contained no water. Isotherm measurements of the monodendron and tridendron series indicated scaling relationships between the area per molecule and the molecular weights of these species.