Abstract: A device is described for obtaining counting and calculating stereological data. The device includes a number of separate counters each of which can be used to accumulate the numerical value of a point count or intersect count made using a test system typically in the form of a matrix of perpendicular lines superimposed over a display of the field to be analysed.The apparatus provides for enlarged real images of the specimen which may be on film or a microscope slide, to be formed on a frosted glass screen on which a test pattern is visible.First computing means is provided for computing from information relating to the test system the numerical values of constants required by a second computing means to convert the numerical values of point or interest counts into numerical values of different parameters of the specimen.