Light spectroscopic properties of fluorescent derivatives of perylene in solvents and lyotropic liquid crystals have been investigated. These were 2,5,8,1l-tetra-tert-butylperylene, methyl 4-(3-perylenyl)butyrate, methyl 3-(3-perylenoyl)propionate, 3-(3-perylenoyl)propionic acid, 9-(3-perylenoyl)nonanoic acid, and N-[9-(3-perylenoyl)nonanoyl]sphingosine-l-phosphocholine. The first two compounds are hereafter referred to as perylenyls, while the latter four are named perylenoyls. Absorption and fluorescence spectra and fluorescence lifetimes of the perylenyls are found to be very similar to those of perylene. Both absorption and fluorescence spectra of the perylenoyls are broadened and red-shifted compared to those of perylene. The fluorescence spectrum is strongly red-shifted with increasing solvent polarity, which is not the case for the perylenyls. Photophysical data of the perylenyl and the perylenoyl molecules in various solvents, micelles, and liquid crystals are given. It is shown that the absorption and fluorescence dipole moments for the S0↔ S1transitions are parallel in both kinds of chromophores. The orientation of these probe molecules in a macroscopically aligned liquid crystal has been obtained from linear dichroism measurements and time-resolved fluorescence anisotropy. It is concluded that the orientation of a probe in its electronic ground state may differ from that in the excited state. Information about rotational motions of the different fluorophores solubilized in micelles and liquid crystals was obtained from the fluorescence anisotropy. The fluorescent moiety of the probe undergoes rotational motions locally in the amphiphile aggregate which are typically about 1–3 ns. A slower correlation time ranging from 10 to 40 ns is ascribed to translational diffusion of the fluorophore in the aggregate. © 1987, American Chemical Society. All rights reserved.