As a step toward a first principles characterization of the optical properties of chlorine hydrate, we have calculated the electronic absorption spectrum of a chlorine molecule trapped in dodecahedral (H2O)(20) and hexakaidodecahedral (H2O)(24) cages. For comparison, spectra were also calculated for an isolated Cl-2 molecule as well as for selected Cl-2(H2O)(n), n <= 8, clusters cut out of the Cl-2(H2O)(20) cluster, allowing us to follow the evolution of the low-lying excited states with increasing number of surrounding water molecules. Although encapsulation of a chlorine molecule within the water cages has relatively little effect on its low-lying valence transitions, it does result in a large number of solvent-to-solute charge-transfer transitions at energies starting near 48 000 cm(-1).