BACKGROUND: Chlorella vulgaris is a green microalgae that contains various pigment components of carotenoids and chlorophylls. Supercritical CO2 is widely used for extraction of pharmaceutical compounds because it is non-oxic and easily separated from extracted material by simply depressurizing. In this work, pharmaceutical compounds from Chlorella vulgaris have been extracted using supercritical CO2 With or without entrainer at various extraction conditions. RESULTS: Based on high performance liquid chromatography (HPLC) analysis, the extracts contained pigment components, such as lutein, beta-carotene, chlorophyll a and b. Higher extraction pressure and temperature promoted higher lutein extraction by supercritical CO2. The optimum pressure and temperature for extraction were obtained as 50 MPa and 80 degrees C. Ethanol as an entrainer was more effective than acetone for the extraction of pigment components. Pigment components in the extract obtained by supercritical CO2 with and without entrainer were compared with the extract obtained by a conventional extraction method. CONCLUSION: Supercritical CO2 has been successfully applied for the extraction of pigment components from Chlorella vulgaris. Supercritical CO2 enabled high selectivity for lutein extraction; however, the lutein yield was lower than that obtained by extraction using supercritical CO2 with ethanol and soxhlet. (C) 2008 Society of Chemical Industry