Dynamic light scattering and viscosimetric methods were used to study polypeptides including polyleucine, poly ( γ -benzyl-L-glutamate), poly ( α -L-glutamic acid), and polyproline II. Chain extension showing rod-like and flexible conformations occurred in poly( γ -benzyl-L-glutamate) and polyproline II solutions as these solutions were diluted in glacial acetic acid or in a mixed solvent of acetic acid and dichloromethane. The elongation of chains in poly( γ -benzyl-L-glutamate) and polyproline II solutions was studied by dynamic light scattering and viscosimetric methods. This nonenzymatic growth of peptide chains provides data on primordial synthesis of protein molecules in the absence of cell machinery and for this reason these reactions may yield valuable data for further studies.