Thin films of aluminum have been produced in the thickness range of 1000–30 Å in small area samples with photoetched edges. The superconducting transition temperatureTc, the critical magnetic fieldHc, and the room‐temperature conductivity have been measured as a function of thicknessd. The results indicate that films as thin as 30 Å act essentially as uniform layers in which the crystal size is approximately equal to the film thickness. The transition temperature was found to vary linearly withd−1.Hc(T) was measured fromTcto 0.4°K. For thickness from 1000 to 200 Å,Hc∼d−3/2, as expected from the Ginzburg‐Landau theory. Ford<200 Å,Hcis paramagnetically limited to about 49 kOe = 19.6Tc, slightly above the Clogston limit.