The volumetric flow rate of liquid and gas though small gigaporous particles was measured by a new method that isolates single particles in a rest apparatus. To our knowledge, this is the first direct confirmation of flow through gigaporous particles made at pressure drops experienced during normal operation. High-performance liquid chromatography particles from 30 to 50 mu m in diameter previously reported to exhibit convection-enhanced intraparticle mass transfer; were studied. Using a CFD model of the rest system the permeability of individual particles was determined from the pressure-drop -flow-rate relationship. The average measured permeability of the particles studied is 7.89 x 10(-15) m(2) with no dependence on particle size. This is 4 to 17 times greater than values calculated from models currently used to estimate the permeability of these kinds of particles. No other experimentally measured values of permeability have been reported for particles of this size. The results of this study might imply that the intraparticle structure does not behave like a bed of uniformly packed mio microspheres, but rather as an inhomogeneous assemblage of microparticles. The measured permeability values offer the possibility of developing better models of the intraparticle flow field under normal operating conditions. Knowledge of the intraparticle flow field is an important step in deriving predictive models of convective mass transfer in these types of particles.