In microscopy, regions of interest are usually much smaller than the whole slide area. Various microscopy related medical applications are liable to benefit greatly from microscope auto positioning in previously defined regions of interest. In this paper we present a method for image-based auto positioning on a microscope slide. The method is based on localization of a microscopic query image using a previously acquired slide map. It uses geometric hashing, a highly efficient technique drawn from the object recognition field. The algorithm exhibits high tolerance to possible variations in visual appearance due to slide rotations, scaling and illumination changes. Experimental results indicate high reliability of the algorithm.