This third in a series of articles deals with the analysis of the dyeing behavior of two mulberry and three nonmulberry varieties of silk. The results of the dyeing tests carried out were discussed in relation to the physical and chemical structure of the silk fibers. Noticeable differences in the dye uptake were observed among the different varieties of silk. Mulberry varieties showed higher dye uptake compared to that of all three nonmulberry varieties. Among the nonmulberry varieties, tasar shows higher dye uptake followed by eri and muga. Interestingly, dye uptake reduces significantly within a variety from the outer to the inner layers. The reduction within a variety was found to correlate well with the morphological parameters. Determination of morphology of fibers confirmed significant differences in structural parameters such as crystallinity, orientation, density, and birefringence, for example, between and within varieties. An increase in all these parameters was observed as one moves from the outer to the inner layers within a variety. The differences in the dye uptake of different varieties of silk correlated well with the physical as well as chemical structure of silk fibers. Dye uptake differences between the varieties were found to correlate with the end amino groups. (C) 2004 Wiley Periodicals, Inc.