Multilayer adsorption isotherms of nitrogen (at 77K), isobutane (at 261K) and neopentane (Z,l-dimethylpropane, at 273K) have been determined on a number of non-porous carbons and silicas. The results serve to strengthen the view that the structure of the adsorbent surface has very little effect on the development of the nitrogen multilayer. The adsorbent structure has a greater effect on the course of the isobutane and neopentane isotherms, but when plotted on a reduced basis the corresponding isotherms for carbon and silica do appear to coincide at p/po > 0.6 and 8 > 2. All the isotherms give linear FHH plots over a wide range of multilayer coverage.