The objective of the audit was to examine how effectively Health manages the risk of PBS drugs not being used according to PBS subsidy conditions. The audit examined two areas: during listing, how Health identified and implemented measures to decrease the risks of PBS drugs being used outside subsidy conditions; and following listing, how Health confirmed that usage and expenditure on PBS drugs was consistent with estimates. The report examines selected approaches used by Health, which have evolved in recent years, to manage the risk of PBS drugs being used outside subsidy conditions. The report also acknowledges and describes the role of the expert committees. The scope of the audit was limited to PBS drugs for which Health pays a subsidy. The audit did not examine Health's role in educating consumers, prescribers, and other health professionals, or the implications of the Australia–United States Free Trade Agreement for the PBS. Additionally, the ANAO did not form an opinion on the success of Medicare Australia's compliance role. To form an opinion against the audit objective, the ANAO interviewed Health personnel, committee members and stakeholders, examined relevant documents and files, analysed drug usage and expenditure data, and attended a number of committee meetings. To assist the audit process, the ANAO selected a sample of eight drugs. The drugs were selected due to their high cost to the PBS and/or high usage, or because the drug has had a particularly interesting PBS history. The sample is not representative of all drugs on the PBS. In 2004–05, 15.3 million prescriptions were written for these eight drugs, with the Government subsidy totalling $1.05 billion.