Cotton fabrics were treated with the sodium hydroxide solution of different concentrations at the varying temperatures. The effects of treating temperature and sodium hydroxide concentration on physical properties and fine structure were studied. Of most of physical properties, especially, drape stiffness showed a greater effect of treatment at the lower temperature for a given sodium hydroxide concentration. On the contrary, tear strength showed a worse effect. Most of fabrics treated with sodium hydroxide solution were transformed from cellulose I to cellulose II slightly. The stiffness of the treated fabrics did not decrease significantly with the washing temperature and the number of washing cycles.