The spectroscopic properties of 4-dimethylamino-4'-bromo-stilbene, 4-dimethylamino-4'-chloro-stilbene were studied by steady-state absorption, emission, polarization spectra and time-resolved emission spectra (TRES) in various solvents at 23 degrees C. A decrease of fluorescence lifetimes was found for all molecules in polar solvents at the blue edge of emission spectra. The lifetimes shorten with decreasing viscosity of solvents. The shift of maximum wavelength of emission spectra of 15-20 nm is observed within the first few hundred picoseconds after excitation. The emission anisotropy r values increase in the vicinity of the 0-0 transition wavelength. A change in the shape of spectra is observed also in some cases. (C) 2009 Elsevier B. V. All rights reserved.