Introduction: Patients' access to medicines can be profoundly affected by the decisions made by medicine licensing bodies and public reimbursement agencies. The present study compares access to licensed and subsidized medicines under a single-payer system in each of the US, the UK, Australia and New Zealand (NZ). These systems are the US Department of Veterans Affairs National Formulary (VANF), the UK NHS for England and Wales, Australian Pharmaceutical Benefits Scheme (PBS) and NZ's Pharmaceutical Management Agency (PHARMAC). The VANF, PBS and PHARMAC all use positive lists of medicines that are subsidized, along with pharmacoeconomic analysis and price negotiations with suppliers. The NHS uses a negative list of medicines that are not to be subsidized, along with pharmacoeconomic analysis of a small number of medicines and caps on manufacturers' profits., Objective: Our objective was to compare licensed and subsidized medicines in terms of the following: (i) total numbers of entities (unique Anatomical Therapeutic Chemical [ATC] codes); (ii) times since first registration (age) of the entities; and (iii) numbers of innovative entities., Methods: This was an observational study in order to test pre-defined hypotheses. All products listed in a major prescribing reference in each country were included in the study. All products were classified by ATC code and their registration dates recorded. Products were collapsed by ATC code to determine 'best-case' licensing and subsidy for each entity, along with the date of first registration. Innovative entities selected for 'fast-track' approval by the US FDA or as a 'breakthrough or substantial improvement' by the Canadian Patented Medicines Prices Review Board were identified. Results were verified by a sensitivity analysis that excluded entities only available in injectable formulations (as these may not always be listed in general prescribing references), and by a parallel analysis done by active agent rather than ATC code., Results: Of the 918 entities and 64 innovative entities licensed in the US, 505 and 20, respectively, were subsidized by the VANF. In the UK, this was 1020 and 58 (1016 and 58 NHS subsidized); in Australia, this was 879 and 49 (567 and 30 PBS subsidized); and in NZ, this was 765 and 39 (503 and 19 PHARMAC subsidized). With the exception of the UK, entities licensed in the US were newer than elsewhere. The median ages were as follows: 6607 days in the US (VANF subsidized 8203 days; p < 0.001); 7319 days in the UK (NHS subsidized 7319 days; p = 0.903); 7795 days in Australia (PBS subsidized 8065 days; p = 0.406); and 8936 days in NZ (PHARMAC subsidized 10 724 days; p < 0.001). NHS subsidized entities were newer than elsewhere. VANF and PHARMAC subsidized entities were significantly older than licensed entities in their respective countries., Conclusion: The single-payer systems examined differ in the number and age of licensed and subsidized entities, along with access to innovative entities. The NHS subsidized the most entities, the newest entities and the most innovative entities. NZ's PHARMAC system subsidized the fewest and oldest entities, and the fewest innovative entities. The VANF and PBS consistently fell between the other two systems in terms of the number of subsidized entities, age of subsidized entities and number of subsidized innovative entities.