The authors obtain the infrared rotation-vibrational spectra of gaseous methanol and acetonitrile and the Raman spectra of liquid ones. The vibrational spectrum of methanol has been analyzed on the basis of Cssymmetry. On the other hand, the vibrational spectrum of acetonitrile has been assigned to C3vsymmetry. The present observations show that the vibrational spectrum of methanol as well as acetonitrile seems to be explained according to C3vselection rules. Because it is in agreement with theoretical expectations for C3vmodel that four parallel type fundamental bands are polarized in Raman and have P, Q, and R branches in infrared, whose P-R separations are observed to be 40 cm−1in CH3OH and 24 cm−1in CH3CN and the agreement of the obtained values with 43 cm−1of CH3OH and 26.7 cm−1of CH3CN calculated on the basis of C3vsymmetry is regarded as satisfactory. In addition, the obtained spectrum of CH3OH shows a marked correspondence to those of CH3CN, CH3Br and CH3I whose symmetry is C3v.