Changes in the structure of electroplated and vapor-deposited copper thin films, as a result of isothermal and isochronal annealing in the temperature range 100-500°C, have been investigated by x-ray diffraction and metallographic techniques. In the electroplated films, recrystallization occurred with an activation energy of about 0.65 eV until the recrystallized grains attained sizes comparable to the film thickness. In vapor-deposited films, such recrystallization is believed to take place immediately after deposition on heated substrates. Grain growth in both sets of copper films proceeded with an activation energy of about 1.55 eV, until a limiting grain size was reached. This limiting grain size is shown to be dependent on the film thickness and the extent of texture present. © 1974 American Institute of Physics.