THE accepted structure of boron nitride, proposed by Hassel1 and Brager2,3, is that of graphite with the carbon atoms replaced by boron and nitrogen atoms, and is designated structure type B.12 in the “Strukturbericht”4. This structure does not give a good agreement between observed and calculated intensities; and as the original work is open to other criticisms, a complete redetermination has been carried out. It is concluded that the Hassel structure is incorrect.