A national war formulary, published during the Second World War, was succeeded by hardback books called British National Formularies (BNFs), which were produced by the British Medical Association and the Royal Pharmaceutical Society about every 3 years until 1976. In 1981 a greatly revised and improved softback version was published and it has been revised and published twice a year since. It has acquired a reputation for being reliable, relevant and up to date. In 2005 the BNF for Children (BNFC) appeared and it has been revised and published every year since. Both BNFs have been used extensively in training prescribers and dispensers, they have supported increasing numbers of 'non-medical' prescribers and overseas use has grown. The current challenge is to provide the BNF data electronically, as three examples show. First, the contents of the BNF and BNFC are available digitally at BNF.org and BNFC.org, and via mobile devices, which require internet access, or as a download, which does not. Secondly, FormularyComplete is a system that enables hospitals, regions, or even countries to create their own formularies, by adding information on costs, local policies and drug availability to an intranet version of the BNF, a data source that cannot be modified. Thirdly, the BNF is working with others to provide the BNF data as computer-readable content, to support electronic prescribing and medicines management. Whatever systems are used, the information on drugs must be reliable and, ideally, all prescribers and dispensers in the UK should be guided by the same data source. [ABSTRACT FROM AUTHOR]