The invention relates to an improved process for the preparation of poly-α-glutamic acids which comprises the polymerization of tertiary γ-esters of α-glutamic acid N-carboxy anhydride with appropriate solvents and initiators, followed by acid hydrolysis of the resulting poly-α-glutamic acid-γ-ester. The process is particularly advantageous in that it allows one to carefully control the molecular weight of the resulting poly-α-glutamic acid. The invention also relates to poly-α-glutamic acids capped at the amino terminus with carboxylic acids or amino acids and to a process for the preparation thereof.