Application of kinetic theory to the process of irreversible thermal denaturation of a biomolecule describes the transformation from a native form A to a denatured form B using a temperature-dependent first-order rate constant, k, in units of s-1. Thermal coagulation in tissues involves irreversible aggregation of denatured biomolecules and may be treated with this simple single-parameter kinetic theory. We present studies in pig liver which document changes in optical scattering as a quantitative measure of coagulation. The results indicate that a distribution of k parameters, not a single k parameter, is needed to describe liver coagulation. The practical implications are that thermal coagulation of liver begins faster than and finishes slower than the predictions based on a single parameter process.