The AlN polytypoid phases in selected materials in the AlN-Al2O3-Y2O3 system has been investigated using TEM methods. Two new AIN polytypoid phases, 24H and 39R, were identified in the pseudobinary AlN-Al2O3 system. The 39R phase existed as single grains while 24H was observed only between subblocks of 33R and 39R. The new polytypoids are built on the same structural models that are previously reported for the other polytypoids in the same system, consisting of arrays of planar (oxygen-containing) and corrugated inversion domain boundaries (IDBs). Only one type of interface structure was observed for the planar IDBs of the new polytypoids.