An endoscopic video system and method using a camera with a single color image sensor, for example a CCD color image sensor, for fluorescence and color imaging and for simultaneously displaying the images acquired in these imaging modes at video rates in real time is disclosed. The tissue under investigation is illuminated continuously with fluorescence excitation light and is further illuminated periodically using visible light outside of the fluorescence excitation wavelength range. The illumination sources may be conventional lamps using filters and shutters, or may include light-emitting diodes mounted at the distal tip of the endoscope.