It was found that organic dyes such as thymol blue, dimidium bromide and methyl orange which are not soluble in pure supercritical CO2, could be conveniently solubilized in AOT water-in-CO2 reverse microemulsions with 2,2,3,3,4,4,5,5-octafluoro-1-pentanol as co-surfactant. The solubilities of these organic dyes in the microemulsions were measured successfully by using a UV-Vis spectroscopy method newly established in our laboratory; besides that, for a given temperature, a critical micelle pressure (CMP) at which formation of AOT water-in-CO2 reverse micelles starts, was determined in term of the effect of pressure on the absorption intensity of the organic dyes in the microemulsions. Furthermore, the micro-polarity environment of the AOT water-in-CO2 reverse microemulsions was investigated systematically according to the shift of solvatochromic probes such as methyl orange and dimidium bromide with varying water content by using UV-Vis spectroscopy. (C) 2004 Elsevier B.V. All rights reserved.