Abstract: A method and apparatus for measuring the permeability, as well as the deliverability, of earth formations traversing a well bore, includes drawing one or more formation flow tests, usually of small volume, from a given formation interval after the region of the formation immediately surrounding the test area is purged of well bore invasion fluid. The purging, done by first drawing a large fluid sample from the formation interval to remove well bore invasion fluid from the immediate area and displace it with connate formation fluid, provides thereby for determining the formation flow properties which obtain with the actual connate formation fluids, as well as for estimating formation damage due to prior invasion of well bore fluid.