A description of fluorescence depolarization spectroscopy in the case of high-aperture-detection and -excitation is considered and described in spherical representation. The formalism outlined applies to one- and two-photon-excitation polarized fluorescence spectroscopy for different kinds of molecular media, including thin layers of organized molecular assemblies, solutions and interfaces. It applies to standard fluorescence and time-resolved linear dichroism measurements, fluorescence microscopy and evanescent-wave-excitation fluorescence experiments. (c) 2005 Elsevier B.V. All rights reserved.