Biodegradable polymeric micelles, self-assembled from a di-block copolymer of poly(D,L-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG), were prepared to achieve folate receptor targeted delivery of doxorubicin (DOX). In the di-block copolymer structure of PLGA-b-PEG, DOX was chemically conjugated to a terminal end of PLGA to produce DOX-PLGA-mPEG, and folate was separately conjugated to a terminal end of PEG to produce PLGA-PEG-FOL. The two di-block copolymers with different functional moieties at their chains ends were physically mixed with free base DOX in an aqueous solution to form mixed micelles. It was expected that folate moieties were exposed on the micellar surface, while DOX was physically and chemically entrapped in the core of micelles. Flow cytometry and confocal image analysis revealed that folate conjugated mixed micelles exhibited far greater extent of cellular uptake than folate unconjugated micelles against KB cells over-expressing folate receptors on the surface. They also showed higher cytotoxicity than DOX, suggesting that folate receptor medicated endocytosis of the micelles played an important role in transporting an increased amount of DOX within cells. In vivo animal experiments, using a nude mice xenograft model, demonstrated that when systemically administered, tumor volume was significantly regressed. Biodistribution studies also indicated that an increased amount of DOX was accumulated in the tumor tissue.