The esterification of poly(gamma-glutamic acid) (gamma-PGA) produced by Bacillus subtilis F2-01 with alkyl halides was carried out at 60-degrees-C in N-methyl-2-pyrrolidinone (NMP) in the presence of sodium bicarbonate to obtain the corresponding esterified gamma-PGA. The thermal properties of these gamma-PGA esters were examined by differential scanning calorimetry and thermogravimetry. gamma-PGA esters were more stable than free acid type gamma-PGA, which decomposed at 210-degrees-C. Melting temperature (T(m)) of gamma-PGA esters could be observed at 230-250-degrees-C. T(m) of gamma-PGA n-alkyl esters reached a maximum at an alklyl chain length of n = 3.