Fourier transform Raman Spectroscopy (Nd:YAG laser at 1064 nm) was used to characterize the four stable phases of 2,4,6,8,10.12-Hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.0(5.9).0(3.11)]dodecane (HNIW, CL-20). Raman spectra are reported over the region from 0-4000 cm(-1). relative to the laser line. A tentative assignment of the most predominant Raman peaks was made with the aid of QM calculations at the B3LYP/6-31G(d) level. A method for detecting polymorphic impurities in epsilon-CL-20 was also developed. The detection level for polymorphic impurities was determined to be below 2%. A method for producing gamma-CL-20 is also presented.