Two conformers of the nonionized alpha-alanine and its isotopomer N,N,O-d(3)-alanine have been observed in low-temperature Ar matrixes. Their infrared spectra have been analyzed and assigned using DFT/B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ geometry and frequency theoretical calculations. Two different intramolecular H-bonds, bifurcated NH2... O=C and N ... H-O, were found in the observed alpha-alanine conformers, I and IIa, We found that the DFT/B3LYP/aug-cc-pVDZ method yields vibrational frequencies of the alpha-alanine conformers in excellent agreement with the experimental data.