The report describes a laboratory investigation into the effect of method of preparation of the test spicemens on the assessment of deformation behaviour of a dense roadbase macadam. Spicemens were prepared from material compacted in a laboratory rolling-wheel compactor, by compacting in a mould using a Proctor Hammer and from material laid and compacted using full-scale equipment. The results of tests under triaxial test conditions were compared for the three types of specimen. Moulded specimens had large variations in density that were not characteristic of those found in the road whereas specimens cored horizontally from material compacted under a rolling wheel were uniform in density. The deformation behaviour of materials compacted in the laboratory under a rolling wheel was found to be similar to that obtained from material cored horizontally in the road pavement. Moulded specimens proved to be much more resistant to deformation. Specimens cored horizontally from material compacted under a rolling wheel are recommended for use in testing designed to study the deformation behaviour of bituminous materials