To provide an electronic endoscope system which can reduce the number of signal lines between an electronic endoscope and an endoscope unit in the electronic endoscope system which has the electronic endoscope designed to output images taken by a solid state image sensor as digital video signals and a processor for the electronic endoscope for outputting the video signals by processing the digital video signals.

The electronic endoscope is so arranged as to write endoscope information on the electronic endoscope into the digital video signals during a blanking period thereof and luminance signals and color difference signals of the digital video signals are made to be multiplexed.