The precipitation of asphaltenes in two Mexican crude oils was measured using a combination of high-pressure isothermal expansion and atmospheric titration with n-alkanes. Experiments were carried out from the live- and tank-oil type of samples of the same crude oils. For the oils investigated, compositional data, precipitation phase diagrams, and bubble point pressures are reported. A theoretical study for these systems was performed using the statistical association fluid theory for potentials of variable range (SAFT-VR) equation of state (EOS) in the framework of the McMillan-Mayer theory. By matching a single titration curve or two precipitation onset points with this EOS, a good prediction of asphaltene precipitation over wide temperature, pressure, and composition intervals is obtained. (C) 2004 American Institute of Chemical Engineers.