X-ray powder diffraction and quantitative texture analysis have been employed to study the crystallographic relation of parent and product phases in direct transformations of graphite-like BN polymorphs into diamond-like BN phases at a pressure of 7.7 GPa and temperatures up to 2600 K. It has been found that the transformation of both CVD-produced bulk slightly textured turbostratic BN (tBN) and highly textured graphite-like hexagonal BN (hBN) results in a preferred orientation of the crystallites of the new cubic BN (cBN) due to the (111)(cBN) parallel to (001)(tBN), (hBN) epitaxial relation. Phase transformation of a CVD-produced bulk highly textured rhombohedral BN (rBN) results in the formation of highly textured wurtzitic BN (wBN) according to the (100)(wBN) parallel to (001)(rBN) crystallographic relation.