In the Borrmann effect, or the anomalous transmission, by diffraction, of x rays through perfect crystals, one state of polarization of the x‐ray beam is preferentially absorbed. Since this happens in the ``transmitted'' as well as in the diffracted beam, a simple polarizer‐monochromator is possible in the sense that insertion and rotation of the polarizer does not sensibly change the line of action of the x‐ray beam. We have used as our ``Borrmann crystal'' a single‐crystal slab of dislocation‐free germanium approximately 30 mils thick and cut for symmetric Laue diffraction from the 220 planes. The details of the rotating crystal holder, an analysis of the polarization, comments on the double‐crystal geometrical effects, and an example of the use of the polarizer‐monochromator to study the polarization term in Bragg diffraction are presented.