The invention is directed to an afocal zoom system, particularly for use in microscopes, comprising at least four optical assemblies, two of which assemblies are movable relative to one another and to the rest of the assemblies for the purpose of changing the magnification. It is the object of the invention to develop an afocal zoom system which enables a relatively small structural size for a microscope also in combination with a suitable drive mechanism. This object is met by an afocal zoom system of the type described above in which every adjustable magnification can be achieved by a displacing movement of the two movable optical assemblies in the same direction.