A detailed study of mixed quantum-classical approximations for radiative and nonradiative processes in condensed phase systems is presented and each approximation is compared to exact fully quantum mechanical dynamics. The problems are formulated in terms of a quantum mechanical time correlation function, and the corresponding mixed quantum-classical descriptions are obtained following the general methodology of Wigner-Kirkwood based on the expansion in powers of Planck＇s constant. Illustrative examples of the performance and applicability of mixed quantum-classical treatments include vibrational and electronic energy relaxation processes, and the calculation of vibronic absorption spectrum.