Calorimetric measurements are expected to provide useful data regarding the relative stability of alpha- versus beta-amino acid isomers, which, in turn, may help us to understand why nature chose alpha- instead of beta-amino acids for the formation of the biomolecules that are essential constituents of life on earth. The present study is a combination of the experimental determination of the enthalpy of formation of N-benzyl-beta-alanine, and high-level ab initio calculations of its molecular structure. The experimentally determined standard molar enthalpy of formation of N-benzyl-beta-alanine in gaseous phase at T = 298.15 K is (298.8 +/- 4.8) kJ center dot mol(-1), whereas its G3(MP2)//B3LYP-calculated enthalpy of formation is -303.7 kJ center dot mol(-1). This value is in very good agreement with the experimental one. Although the combustion experiments of N-benzyl-alpha-alanine were unsuccessful, its calculated enthalpy of formation is -310.7 kJ center dot mol(-1); thus, comparison with the corresponding experimental enthalpy of formation of N-benzyl-beta-alanine, -(298.8 +/- 4.8) kJ/mol, is in line with the concept that the more branched amino acid (alpha-alanine) is intrinsically more stable than the linear beta-amino acid, beta-alanine.