[en] Laser Raman spectroscopy was used to identify the crystal structures of lanthanide and actinide compounds. The phonon Raman spectrum is characteristic of the particular crystal structure. GdCl₃ exhibits two crystal structures, the UCl₃-type hexagonal and the PuBr₃-type orthorhombic. In the literature it is reported that the low temperature form is orthorhombic; results of experiments here suggest that it is hexagonal. Interconversion between these two forms can be accomplished with temperature andor pressure. In the present work laser Raman spectrometry was used to monitor crystal structure changes in GdCl₃ as a function of temperature or pressure to determine the temperature or pressure at which the hexagonal-to-orthorhombic transformation occurs. Raman spectroscopy was also used to determine the symmetry assignments for the Raman-active bands of a single crystal. Raman spectra of polycrystalline NdBr₃ have been recorded at room temperature and pressure and at approximately 100/degree/K. In addition, polarized Raman spectra of a single crystal NdBr₃ have been measured. Based on these polarization measurements, symmetry assignments of eight Raman-active modes were made. These assignments are useful in interpreting the phonon Raman spectrum of any compound exhibiting the PuBr₃-type orthorhombic structure. 24 figs., 5 tabs