A poly(aspartic acid)-block-polylactide- (PAsp-block-PLA) diblock copolymer was synthesized through the polymerization of beta-benzyl-L-aspartate-N-carboxyanhydride [Asp(OBzl)-NCA] with amino-terminating polylactide (NH2-PLA) as a macroinitiator. The chain length of the PAsp segment could be easily controlled by changing the. monomer/initiator ratio. Dynamic light scattering measurements of PAsp-block-PLA aqueous solutions revealed the formation of polymeric micelles. Changes in the micelles as a function of pH were investigated.