Abstract: An X-ray collimator in an X-ray analysis apparatus, consisting of plates of X-ray absorbing material, for example tungsten, which are arranged transversely of the X-ray beam. The plates are identical and provided with a pattern of rows and columns of rectangular openings 40, 42 which have a vertical period p.sub.1 and a horizontal period p.sub.2. The openings take up an opening fraction t.sub.1 and t.sub.2 of the periods p.sub.1 and p.sub.2, respectively. The plates are arranged in the collimator in a series in which the ratio between two successive distances (d.sub.i, d.sub.i+1) between the plates of the series is equal to the given opening fractions t.sub.1 and t.sub.2 of the periods p.sub.1 and p.sub.2, respectively. It has been found that all directions in the X-ray beam are then intercepted except for the direction to be collimated. Moreover, this configuration also enables transverse collimation.