Digest 427 brings up-to-date the information contained in Digests 274 and 275 which are now withdrawn. The scarcity and cost of suitable land is leading to the development of sites where there are deep deposits of fill. Occasionally cases are reported where serious failures have occurred. These reports should not obscure the fact that many buildings have been successfully built on fill; they emphasise the importance understanding the behaviour of fills, identifying potential hazards and adopting measures that will ensure successful development of these sites. 12 pages.