The crystallization of disordered and partly disordered cellulose on hydrolysis with boiling dilute mineral acid was studied and the level-off degree of polymerization (LODP) of cotton after treatment with inter-or intracrystalline swelling agents was determined. The LODP, of cotton and of cotton which had been swollen in morpholine were similar, indicating that the LODP of cotton cellulose was not affected by this intercrystalline swelling agent. It appears that the aggregates of cellulose chains present in cotton which has been treated with aqueous NaOH of mercerizing strength and then washed with water are not uniformly accessible to hydrolyzing acid and that the accessibility to the acid is not changed when the cellulose is dried. The LODP of samples of mercerized, ethanol-washed, never-dried cotton that had been acetylated was obtained and the results are discussed in terms of current views on the fine structure of cotton.