Influence of hydrostatic pressure on the reversible polymerization of human sickle cell hemoglobin (which has a negative temperature coefficient of gelation) has been investigated in order to derive the volume of activation in the process. Parallel investigation has been done with blood clotting protein (fibrin), which has a positive temperature coefficient of polymerization. It has been found that the volume of activation for S hemoglobin polymerization is 100 cc per mole and for fibrin 70 cc per mole. The study must be extended further to include the following: effect of concentration of respective proteins, effect of pH, and temperature. This type of investigation will give us further insight into the nature of protein-protein interactions and the topological problems involved in the problem of polymerization still not well understood.