"The decade between the 1981 and 1991 UK Censuses of Population has seen an enormous increase in the use of the postcode system for locational referencing. To date, no direct means have existed for linking postcoded data to census geography at the most detailed level, but the production of a new ED/postcode directory promises to offer a range of new opportunities for postcode applications following the release of the 1991 Census data. This paper reviews the characteristics of the postcode system, describes the new directory, and examines the methods which will be available for linking the Census and postcodes post-1991."