Abstract The rotatory dispersions and ultraviolet absorption spectra of six homologs of 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl alkylxanthates have been measured, and the effects of the alkyl groups on the rotatory dispersion have been discussed by comparison with the case of the sugar xanthates already studied by Tsuzuki et al. (Bull. Chem. Soc. Japan, 37, 162, 730 (1964)). All show positive Cotton effects, the molecular amplitude of which diminishes with an increase in the number of carbon atoms of the alkyl group, while the molecular extinction coefficient decreases as the carbon number of the alkyl group increases from 1 to 4. These facts agree with the earlier findings and can be interpreted in terms of the relation, R=μcosθ\sqrtD, between the electron transition, the rotational strength, and the dipole strength given by S. F. Mason (Quart. Rev., 17, 20 (1963)).