Soybean oil and olive oil were investigated as continuous co-solvents for supercritical carbon dioxide (SC-CO2) extraction of astaxanthin from Haematococcus pluvialis. Without co-solvents, only 25.40 +/- 0.79% efficiency was achieved with SC-CO2 extraction at 70 degrees C and 40 MPa at a continuous flow rate of 3 mL min(-1) for 5 It. In the presence of soybean oil or olive oil as a co-solvent, the extraction efficiency was enhanced, with the most appropriate level of soybean oil in the solvent mixture being 10% by volume. At this concentration and the above extraction conditions, the highest extraction efficiency of 36.36 +/- 0.79% was obtained for soybean oil, a 30% increase in extraction efficiency compared with SC-CO2 extraction without soybean oil, whereas the 10% olive oil increased the extraction efficiency further to 51.03 +/- 1.08%, which was comparable to that obtained using ethanol as co-solvent. (C) 2007 Elsevier Ltd. All rights reserved.