All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Comparison of Average and Point Capillary Pressure-Saturation Functions Determined by Steady-State Centrifugation Soil Physics T he capillary pressure-saturation function is an important hydraulic property of variably saturated rocks and soils. Th is function is needed for simulating multiphase fl uid fl ow and chemical transport in porous media in applications such as agricultural crop production, enhanced oil recovery, subsurface C sequestration, and remediation of contaminated soils. In soil physics, the capillary pressure-saturation function is traditionally determined in the laboratory using a hanging water column (Dane and Hopmans, 2002a) or pressure plates (Dane and Hopmans, 2002b). In these methods, a series of capillary pressures, ψ, are imposed at a particular point and the corresponding volumetric water contents for the entire porous medium, 〈θ〉, are determined gravimetrically or manometrically. If the densities of the nonwetting and wetting fl uids are diff erent, ψ will vary with height within the porous medium (Dane et al., 1992; Liu and Dane, 1995a). As a result, the volumetric water content at the point where ψ is controlled, θ, can deviate signifi cantly from the measured 〈θ〉. Th us, use of the capillary pressure-average saturation function, 〈θ〉(ψ), instead of the point capillary pressure-saturation function, θ(ψ), in fl ow and transport models can produce erroneous predictions of important hydraulic properties such as the relative permeability function (Peters and Durner, 2006). Because point measurements of θ are rarely available in hanging water column and pressure plate experiments, computational procedures have been developed to extract the θ(ψ) function from the measured 〈θ〉(ψ) function. Liu and Dane