AbstractTen series of model filaments with increasing orientation and swelling degrees ranging between 16 and 1.2 were prepared from three viscoses containing 4, 6, and 10.5% cellulose. Their birefringence was measured and their x‐ray diagrams taken and quantitatively evaluated in order to determine the over‐all orientation of the iiber substance and that of the crystalline portion. It is shown that a general relation exists between the orientation of the crystallites and that of the entire fiber substance which is the same in all fibers stretched in the swollen state. Once the birefringence of a filament is known, the orientation factor of its crystallitee can be computed without taking an x‐ray photograph. From the data further evidence can be derived to the effect that the orientation of the crystallitm cannot be accounted for by the theory of affined deform