Assessments of dew-, water-, and enzyme-retted fibers for differences in fineness, strength, caustic weight loss, acid detergent fiber, neutral detergent fiber cellulose, hemicellulose, lignin, carbon, hydrogen, nitrogen, lipid, ash, and nine minerals were compared in this study. Distinct differences in retted-fiber samples were observed in all the parameters tested. The samples also were analyzed by derivative thermogravimetry, which revealed that weight losses in two decomposition bands of 240-400 degrees C and 400-520 degrees C correlated with the fiber fineness and the caustic weight-loss measurements of the samples. The variations in quality of the fiber samples were mainly due to differences in the proportion of residual noncellulosic polysaccharides, lipid, lignin, and certain minerals. The key parameters for determining fiber quality are fiber fineness, strength, ash, caustic weight loss, and the derivative thermogravimetry weight-loss parameters.