In the latter part of the 1920’s we began to understand more and more the phonological system of the Athapaskan languages, mainly through the efforts of Edward Sapir. It was the belief then that the Proto-Athapaskan phonological system, particularly the consonantal system, can be fairly accurately reconstructed. For many years my friend Harry Hoijer has carried this type of comparative study further by including a number of languages hitherto not available, so that the comparative study of Athapaskan languages has become one of the best explored fields in North America. There are of course many problems which remain to be solved, such as the vocalic system, the vocalic lengths, the development of pitch or the loss of it, and other problems of morphology. It is the purpose of this paper to draw attention to some of these problems, rather than to solve them.