The gerund here studied is a grammatical form of great interest on account of its phonological variations and the wide range of its syntactical relationships. It occurs in the single form, gide, in a strengthened form, giderek, and in a pair form, gide gide. We find it as an independent gerund and in verbal combinations which vary from mere association to complete fusion, such as gidememek and gideyor (gidiyor). It also has a tendency to become specialized in use as a post-gerund, and numerous particles have originated in this way. It has had a long history, being one of the basic grammatical forms of Turkish, a common feature of the Turkish family of languages from the time of the early inscriptions of northern Asia. In Ottoman Turkish its importance (except in the -erek and pair forms) has gradually declined during the last 500 years, and it is now used only to a very limited extent; but in Old Ottoman it was fairly widely employed, and the texts which have survived provide ample material for study. It is, however, a complicated study. In the work which has been done it would seem that investigators have usually relied on insufficient data, or have applied methods unsuitable for this case. For example, the method of general comparison between Ottoman on the one hand and various speech forms such as Uighur, Chaghatai, and modern Anatolian dialects on the other, cannot give satisfactory results. There are too many unknown factors, too many imponderables. Such a procedure inevitably leads to the comparison of mere isolated examples which do not really prove anything. I have therefore confined myself to Old Ottoman, and my method has been to take whole texts and collect and classify all the examples of this gerund which they contain. This is laborious, but it produces results which cannot be obtained in any other way.