Abstract: The invention is a method of determining the permeability of an earth formation using a wireline formation testing instrument. The method includes measuring pressure with respect to time at a probe in hydraulic communication with the earth formation, calculating time derivatives of the measured pressure, withdrawing fluid from the earth formation by increasing a volume of a chamber in hydraulic communication with the probe, measuring the volume of the chamber with respect to time, and calculating time derivatives of the measured volume. Increasing the volume of the chamber is stopped. The permeability is calculated when the measured pressure substantially stops increasing, by determining a slope of a linear relationship of the measured pressure with respect to a fluid flow rate calculated from the time derivative of the volume and the time derivative of the pressure.