Using the steady-state centrifuge apparatus, we have conducted an experimental test that strongly supports Darcy's law, only the second published rigorous test of this law for unsaturated soil, and the only one for a medium far from saturation and for a large (factor-of-10) range of driving forces (Nimmo and others, 1987). A later experiment tested Richards' equation under low-water-content conditions (Nimmo, 1990). This experiment, using a custom-modified centrifuge and unique apparatus, showed Richards' equation to adequately describe a particular set of transient flow conditions within usual unsaturated-flow accuracy, even below 25% saturation. The same study also tested and applied a newly formulated relationship between soil electrical conductivity and water content, demonstrating a new technique for measuring dynamically changing water content in small samples.