In order to understand the origin of ultrafast carotenoid bandshifts upon photoexcitation of bacteriochlorophyll (BChl) molecules in antenna complexes of photosynthetic purple bacteria, we have performed sa-CASSCF(8,7)/6-31G land 6-31G*) calculations for the low-lying excited states of the carotenoid rhodopin glucoside (RG). The LH2 environment was simulated via atomic point charges to represent the electrostatic field of the ground and the Q(y) excited states of BChls near the carotenoid. The calculations showed that excitation of the B800 BChls yields a significant blueshift of the carotenoid S-2 energy in good agreement with experiments. We also found that the lowest triplet state energy of the RG is below 0.78 eV, which is lower than the energy of O-1(2)* (0.97 eV), in accord with the role of carotenoids as photoprotectors.