Using a literature compilation of melting point and fusion enthalpy data from over 700 organic compounds it is shown that the entropy of fusion, Delta S-f, is dependent upon the enthalpy of fusion, Delta H-f. 'Flexible' molecules (those that are potentially multi-conformational tend to yield higher values of Delta S-f for a given Delta H-f, than do 'rigid' ones. The overall dependency is roughly linear and gives a positive intercept on the entropy axis. This is identified with Delta S-to, the entropy gained from onset of translational and orientational freedom on melting. The enthalpy dependent component, Delta S-h, is considered to arise by analogy with entropy-enthalpy compensation in ligand binding processes. Because of the way the Delta H-f distribution is truncated in typical 'random' selections of chemical compounds, dependency inevitably leads to kurtosis of the Delta S-f value distribution and this is augmented by kurtosis in Delta H-f and molecular weight. These are the main reasons for the often observed 'constancy' of Delta S-f for 'rigid' molecules which is termed Walden's Rule. This rule has therefore no general validity. 'Flexible' molecules usually possess additional entropy, Delta Sc, from the release of conformational disorder in the melt. Their relative position on the Delta S-f/Delta H-f plot can indicate the magnitude and extent of such disorder. For instance the situation of n-alkanes suggests relative conformational freedom but n-alkyl theophyllines appear to be constrained. Molecules with strongly hydrogen bonding groups (donor and acceptor),even with n-alkyl groups, have lower relative Delta S-f, presumably due to association.