Amphiphilic AB block copolymers of 2-(dimethylamino)ethyl methacrylate (DMAEMA) with methyl methacrylate, methyl acrylate, or styrene have been synthesized by atom transfer radical polymerization using well-defined poly(methyl methacrylate), poly(methyl acrylate), and polystyrene as macroinitiators. The molecular weight distributions of the block copolymers are very narrow (M-w/M-n similar to 1.2). Kinetic studies indicate the block copolymer formation is a controlled process with molecular weight increase linearly with the conversion. Block copolymers containing different lengths of PDMAEMA segment can be easily prepared by varying the ratio of DMAEMA and macroinitiator. ABA triblock copolymers of PDMAEMA-PMMA-PDMAEMA have also been prepared using difunctional PMMA macroinitiator. Clean chain extension to form block copolymer has been achieved when PMMA and PMA were used as the macroinitiators. The molecular weight distributions of the resulting block copolymers are fairly narrow. However, a less complete chain extension from PSt to PDMAEMA was observed due to the relatively slow initiation compared to propagation and/or the presence of the side reactions.