Adsorption of argon, krypton, nitrogen, and hydrogen on an iron film, and of krypton, nitrogen, and hydrogen on a titanium film and on catalyst sponges of iron and titanium has been investigated at 76–154 K. In addition, the sorption of nitrogen at 473–773 K by the titanium film has been compared with that of the sponge. At low temperatures argon, krypton, and nitrogen isotherms are of BET type II shape, but for hydrogen they are either linear or of type III. Isosteric heats of adsorption at 76–113 K indicate that all the gases are physically adsorbed in this temperature range, there being no significant difference between films and sponges. In the initial stages of equilibration of each dose of nitrogen at 473–773 K, the rate of sorption by both forms of titanium follows a parabolic law, and this subsequently changes to a logarithmic law. The film has a considerably greater capacity for nitrogen sorption than the sponge; at 563 K and 0·23 Torr, the film sorbs 10·2 monolayers, whereas at 573 K and 1·0 Torr the sponge sorbs 0·32 monolayer. The heat of solution of nitrogen in titanium is estimated to be –163 kJ mol^–1.