Poly(L-serine) is a poly(amino acid) having a side group (-CH2OH). It is found to exist in an anti-parallel beta sheet structure. A study of complete normal modes and their dispersion has been carried out using Higg’s modification of Wilson’s GF matrix method and the Urey-Bradley force field. The constants of the field have been best fitted to the Fourier transform infra-red and Raman frequencies. Repulsion and exchange df character between various pairs of modes have been observed. Heat capacity as a function of temperature, obtained from the dispersion curves via density-of-states, is in good agreement with the measurements of Roles et al. (Biopolymers, 1993, 33, 753).