Abstract: An apparatus and method for determining the minimum miscibility pressure of a system comprising a gas and a liquid. A liquid-filled tube is equilibrated at a predetermined temperature and initial pressure, and pressure changes are determined as a single gas bubble is launched, rises through the tube, and stabilizes in the liquid. The measurements are repeated with fresh liquid at a series of different predetermined pressures. The minimum miscibility pressure is obtained either by finding the final pressure at which the time between launch and stabilization is constant or by evaluating the derivative of an empirically derived relationship between initial pressure and final pressure.