This work investigated the high-pressure phase behavior of systems containing glycerol, olive oil and propane in the presence of surfactant AOT. The static synthetic method, using a variable-volume view cell, was employed for obtaining the experimental data in the temperature range from 298 to 373 K, and pressures up to 30 MPa. First, the effect of addition of AOT on the vapor pressure of pure propane was investigated and then the effect of addition of AOT to mixtures of propane + glycerol. Measurements were afterwards accomplished for the system propane + AOT + glycerol + olive oil. For the ternary system liquid-liquid (LLE) and vapor-liquid-liquid (VLLE) equilibrium were observed. Besides VLE, LLE and VLLE, the quaternary system propane + AOT + glycerol + olive oil exhibited at higher concentrations of the glycerol/olive oil ratio a fascinating phase behavior, with the occurrence of three (LLL) and four (VLLL)-phases in equilibrium. (c) 2006 Elsevier B.V. All rights reserved.