Resistivity measurements have been performed in a combined LEED/Auger apparatus on thin copper films deposited at room temperature on Si(111) substrates under UHV conditions. The resistivity changes during annealing are related to the film structure. Two steep rises in the resistivity vs. temperature curves are observed at 125 and 250 degreesC which can be attributed to a coagulation of the copper film and silicide formation. respectively. The results are compared with optical data previously obtained by ellipsometrical measurements on the same films.