Using a water substitution method to determine bed voidage, an independent relationship between bed height and bed voidage was observed for the trilobe (virgin and crushed) and cylindrical alumina supports. Typical bed voidage values of 0.49-0.51 (virgin trilobe). 0.46-0.52 (crushed trilobe) and 0.28-0.31 (cylindrical) were observed within 0.1 and 0.19 m i.d. columns. However, bed voidage values were approximately 6% larger in the 0.05 m i.d. column and could be attributed to a greater extent of wall zone voidage. Dense packing of the columns in all cases resulted in a decrease in bed voidage which had significant effects on bed density and column pressure drop, in addition to the water substitution measurements of bed voidage, three-dimensional magnetic resonance imaging (MRI) data were used in conjunction with digital image analysis techniques to obtain one-dimensional radial profiles of voidage from comparable alumina catalyst support material. Similar results and trends in voidage values between the water substitution method and those obtained from MRI data are evident. In all cases, the analysis of the MRI data yields voidage values that are consistently higher than those obtained from water substitution measurements.