The use of low energy X-rays, up to 30 keV, densitometry is demonstrated for grain flow rate measurements through laboratory experiments. Mass flow rates for corn were related to measured X-ray intensity in gray scale units with a 0.99 correlation coefficient for flow rates ranging from 2 to 6 kg/s. Larger flow rate values can be measured by using higher energy or a higher tube current. Measurements were done in real time at a 30 Hz sampling rate. Flow rate measurements are relatively independent of grain moisture due to a negligible change in the X-ray attenuation coefficients at typical moisture content values from 15 to 25%. Grain flow profile changes did not affect measurement accuracy. X-rays easily capture variations in the corn thickness profile. Due to the low energy of the X-ray photons, biological shielding can be accomplished with 2-mm-thick lead foil or 5 mm of steel. (C) 2000 Elsevier Science B.V. All rights reserved.