The primary object of the work described was to examine the dependence of the equilibrium water content of cellulose (viscose) filaments on applied tensile stress. For both isotropic and oriented filaments a reversible increase of water content with tensile stress was observed, this effect being in the direction required by thermodynamic theory, and of the expected order of magnitude. A precise quantitative test of the theory was not possible, on account of the imperfectly elastic behavior of the material. Subsidiary experiments are reported on the variation of length with relative humidity, and on the vapor pressure isotherms, for isotropic and oriented cellulose. It is shown that, for the isotropic material, the longitudinal swelling can be accurately calculated from the water content, using P. H. Hermans' density data; this calculation, incidentally, provides a useful check on Hermans' figures. Finally, a figure is derived for the water absorption by the isotropic cellulose in contact with liquid water. -- AATA