Test procedures for determining the acceptability of fills for earthworks compaction require the removal of particles larger than a predetermined maximum size prior to test. In particular, the use of the Moisture Condition Apparatus requires that stones, defined as particles larger than 20 mm, are removed from the test sample. Many tills contain a significant proportion of such stones. Consequently, the relevance of the results of tests carried out on the remaining, or matrix, material can be questioned. An extensive laboratory test programme has been carried out to determine the effect of oversize particles on the compaction behaviour of soils. The results indicate that the transition from behaviour determined by the matrix to behaviour determined by the stones occurs at approximately 45% to 50tone content. Below this stone content, conventional techniques may be used for determining acceptability for earthworks compaction. However, if the behaviour is determined by the stones, then a series of alternative approaches are recommended for use depending on the nature of the soil and the type of compaction control specified.