The aims of this investigation were to develop a procedure to prepare and characterize docetaxel encapsulated PEGylated liposomes using supercritical carbon dioxide as antisolvent and optimize the process and formulation variables using response surface methodology. The process and formulation variables were optimized by "Box Behnken Design (BBD)" of response surface methodology (RSM) with temperature, pressure and CO2 flow rate as independent variables and particle size and yield as dependent variables for process variables while the amount of hydrogenated soya phosphotidylcholine (HSPC), soya phosphotidylcholine (SPC) and cholesterol as independent variables and % entrapment efficiency as dependent variables for optimization of formulation variables. The optimized liposomal formulation was characterized for particle size, shape, morphology, crystallinity, zeta potential, % entrapment efficiency, residual solvent content and in vitro drug release. The process and formulation variables were optimized to achieve maximum drug entrapment efficiency and yield. Results for particle size, zeta potential, % entrapment efficiency and in vitro drug release of PEGylated liposomes were found to be 269.2 +/- 2.8 nm, -27.2 +/- 1.8 mV, 79.2 +/- 4.4 %w/w and 37.5 +/- 4.5% in 24 h, respectively. The liposomes were found to be small, unilamellar and spherical with smooth surface as seen in photomicrographs of scanning electron microscopy and transmission electron microscopy. Differential scanning calorimetry and X-ray diffraction results indicated a molecular dispersion of docetaxel in the liposomes. In this study, supercritical fluid technology was successfully used to prepare small, spherical and unilamellar liposomes of docetaxel with high entrapment. It was observed that supercritical fluid technique can be an excellent technique for preparation of docetaxel liposomes which otherwise is very difficult to prepare as a solvent free and stable liposomes. (C) 2010 Elsevier B.V. All rights reserved.