The combination of time-dependent d. functional theory (TDDFT) for the description of excited states with a hybrid quantum mechanics/mol. mechanics (QM/MM) approach enables the study of photochem. processes in complex environments. Here, we present a short overview of recent applications of TDDFT/MM approaches to a variety of systems including studies of the optical properties of prototypical org. and inorg. mols. in gas phase and soln., photoinduced electron transfer reactions in donor-bridge-acceptor complexes, and in situ investigations of the mol. mechanisms of photoactive proteins. The application of TDDFT/MM techniques to a wide range of systems enables an assessment of the current performance and limitations of these methods for the characterization of photochem. processes in complex systems. [on SciFinder (R)]