The effect of solvent electrostatics and solute torsional modes on the absorption spectrum of betaine-30 in acetonitrile is examined. Combined quantum/classical molecular dynamics ground state simulations are used to calculate the electronic absorption spectrum in acetonitrile. The model for betaine-30 includes the electronic degrees of freedom of the pi system of the molecule and their interactions with the electric field of the solvent, treating the electronic wave function at the level of Pariser-Parr-Pople semiempirical electronic structure theory. The absorption intensity, width, and maximum of the S-0 to S-1 band are well reproduced by the model. In solution, the So molecular dipole moment is found to be strongly enhanced due to solvent-induced electronic reorganization. The width of the absorption band in acetonitrile is found to be a function of solvent orientational fluctuations and is not correlated with conformational changes caused by torsional motion in the molecule. This fact, combined with the good agreement between the classical reorganization energies inferred from the simulated and experimental spectra indicates that, at least in acetonitrile, the classical component of the reorganization energy is fully determined by solvent orientational polarization. The spectral band maximum of the lowest energy transition is found to be blue shifted over 7000 cm(-1), compared to a calculation in which the coupling of the betaine-30 electronic structure to the solvent molecules is eliminated, in agreement with the shift found experimentally for betaine-30 in acetonitrile compared to alkanes. However, in contrast to the result found in acetonitrile, the transition energy in the absence of solvent interactions is found to be strongly correlated with the central phenolate-pyridinium dihedral ring angle. This contrasting behavior implies that in nonpolar solvents, the classical reorganization energy does have a contribution from that torsional mode. Correspondingly, this difference in behavior with solvent indicates that the assumption of a solvent independent intramolecular contribution to the reorganization energy is questionable.