A block copolymer based on poly(gamma-benzyl-L-glutamate) (PBLG) as the hydrophobic part and poly(ethylene oxide) (PEO) as the hydrophilic part was synthesized and characterized. PBLG/PEO/PBLG (GEG) block copolymer nanoparticles were prepared using the dialysis technique. Fluorescence spectroscopy measurement suggested that GEG block copolymers were associated in water to form polymeric micelles and the critical micelle concentration (CMC) value of the GEG-50 block copolymer was 0.0084 g/L. Particle-size distribution of the GEG-80 block, copolymer based on the number average was 34.9 +/- 17.6 nm. Also, the particle size and drug-loading contents of GEC nanoparticles were significantly changed with the initial solvent used. From transmission electron microscope (TEM) observations, the GEG polymeric micelle was a nice spherical shape and the sizes ranged from approximately 20-60 nm in diameter. Results from assessing the drug-loading contents against the initial solvent showed that the use of tetrahydrofuran (THF) or 1,4-dioxane as the initial solvent resulted in higher drug-loading contents than those of other solvents. In the drug-release studies, the higher the molecular weight of the polymer and drug-loading contents, the slower the drug release. Also, the initial solvent used was significantly affected not only in the drug-loading contents but also in the drug-release kinetics. (C) 2000 John Wiley & Sons, Inc.