The effect of I-propanol, n-pentanol, n-heptanol, and benzyl alcohol on the phase behavior Of CO2/Ls-54 system has been investigated. The results indicate that the alkyl chain alcohols can reduce the cloud point pressure (CPP) considerably, and the smaller alcohols are more effective. However, addition of benzyl alcohol leads to increase in CPP. In addition, the phase behavior study of Ls-54 surfactant in supercritical (SC) CO2 with different n-heptanol concentration was also carried out. The results showed that the CPP increases with increasing temperature and decreases with increasing n-heptanol concentration. (C) 2003 Elsevier B.V. All rights reserved.