AbstractThe force as a function of temperature at constant length for cellulose model filaments swollen in water shows a maximum the temperature of which decreases with increasing orientation. At an orientation achieved by a prestretch of 80%, no more maximum exists, and the force decreases monotonically with increasing temperature. This behavior cannot be attributed to changes in the entropy and enthalpy of elongation with temperature, but is due rather to changes in the degree of swelling. When corrections are made for this, the positive force‐temperature coefficient observed for some of the curves becomes negative. The equilibrium stress‐strain curves are linear up to elongations of 5%. The‐oretical evaluation of these curves is not possible with the present state of theory. Filaments with predominantly a skin structure show a minimum in the force‐temperature curves; this is the more common b