A significant amount of data exists for the phase equilibria of pure n-alkanes in supercritical propane, yet no data is available for mixtures of n-alkanes in supercritical propane. In this work experimental measurements of the solubility of a mixture of alkanes in supercritical propane was conducted and the principle of congruence is applied to link the pure component and mixture behaviour. Experimental measurements show that the principle of congruence can be applied successfully to high-pressure phase equilibria of n-alkanes in supercritical propane, especially in the bubble and dew point region. In the mixture critical region, although the solubilisation pressure of the mixture is approximately 10% lower than that of the pure alkane, it provides a good order of magnitude estimation. (C) 2006 Elsevier B.V. All rights reserved.