A reliable method of determining the moisture content of bulk wheat grain samples has been established. By compressing the grain seed into a self-supporting bulk sample, the determination of the complex permittivity has been simplified; waveguide windows and high-Q cavities of previous techniques are not necessary. Measurement of the real and imaginary parts of the complex permittivity of the bulk grain samples, in a standard waveguide cell, showed that they are suitable indicators for determining the moisture content of the grain. Furthermore, the complex permittivity, both real and imaginary, is independent of the force applied to compress the grain and so the compression process control does not impinge on the accuracy of the measurement of the grain moisture content. (c) 2006 Elsevier Ltd. All rights reserved.