Abstract: An apparatus for fluorescence diagnosis comprises an illumination system for illuminating a target area. The observation system has an observation instrument and a camera. The illumination system can be switched between at least two illumination modes. The observation system has an optical arrangement having at least one optical element that selectively can be introduced into the observation beam path or can be removed therefrom in order to switch the optical properties of the observation system between at least two observation modes. The optical arrangement of the observation system has a motor drive for introducing the at least one optical element into the observation beam path and for removing said element therefrom, and there is a control unit which is connected to the illumination system and to the observation system and which controls the motor drive as a function of the set illumination mode of the illumination system.