The influence of hydrogen bonding, hydrophobic and electrostatic interactions on the thermal stability of rat tail tendon collagen fibre has been studied using differential scanning calorimetry (DSC) and hydrothermal isometric tension (HIT) experiments. The reagents used to study these effects are urea (hydrogen bonding), aqueous alcohols (hydrophobic) and 0.02 M Tris-maleate buffer at pH 4-8 (electrostatic interactions). The peak temperature, enthalpy changes and energy of activation for collagen to gelatin transition are computed using DSC. The peak temperature and enthalpy changes decrease with increasing concentrations of urea, increasing chain length of alcohol and decreasing pH. The shape of the isometric tension curves of the collagen fibres provide information on the crosslinking of collagen fibre while the extent of relaxation after maximum tension is indicative of thermally stable crosslinks.