The K x-ray absorption discontinuities of copper, gallium and germanium in pure metals as well as in six copper-gallium and three copper-germanium alloys have been studied using a Cauchois-type bent crystal spectrograph. It is observed that in all the systems the K discontinuity of copper shifts towards the higher energy side, while the discontinuities of gallium and germanium shift to the lower energy side relative to their positions in the respective pure metals. The magnitudes of the shifts are found to increase with the decrease in the content of the absorbing atom in the alloys. The observed shifts are explained on the basis of the free-electron theory of metals and the rigid-band model for alloys.