Statistical mechanical principles are used to derive the approximate relationship of c(1) + c(2)ln(n) + c(3)n for the entropy of homo-oligo peptides with n residues, where c(1), c(2) and c(3) are constants for a specific polypeptide chain. The relationship is tested in the range 1 <= n <= 34 against entropy data derived from electron structure calculations completed both at the Hartree-Fock and the density functional levels of theory. We have found that the above equation provides a good representation of the entropy of oligoglycine and oligoalanine model systems when they fold from an extended-like to a helical conformation. (C) 2010 Elsevier B. V. All rights reserved.