A room temperature Raman study has been performed on the following compounds: EtNH3X (X=Cl,Br), CD3CH2NH3Cl, CD3CH2ND3Cl, CH3CD2NH3Cl, CH3CD2ND3Cl, and EtND3Cl. The complete vibrational spectra are discussed in terms of external and internal modes. The external modes of the halogens have been identified on the basis of the isotopic substitutions. The internal vibrations are divided into three frequency ranges. Several modes are clearly identified through the observed isotopic shifts, while other modes are found to interact strongly. The Fermi resonances of the carbon–hydrogen stretching modes with the carbon–hydrogen deformational modes are analyzed.