The steric effect of solvent molecules in the dissolution of polyacrylonitrile (PAN) from five different kinds of N,N-dimethylformamide (DMF) derivatives was studied using Raman spectroscopy and a laboratory constructed laser optical instrument. The dissolution behavior of PAN from solvents such as DMF, N,N-dimethylacetamide, N,N-diethylformamide, N,N-dimethylcarbamylchloride, and N,N-dimethyltrichloroacetamide was studied with the laser optical method. Raman spectra of the solvents and solutions provided significant information on the intermolecular interaction between nitrile and the solvents (i.e., dipole-dipole interaction). The carbonyl band in each solvent shifted from a lower to a higher frequency when nitriles were added, and the extent of the shift was directly related to the structure and geometry of a subtituent in each solvent molecule. An inverse linear relationship between the value of the dissolution temperature (T-sol) and the extent of the Raman carbonyl shift is demonstrated. It seems reasonable to explain this in terms of the steric effect of solvent molecules in the dissolution of PAN.