Reference price systems for prescription drugs have found widespread use as cost containment tools. Under such regulatory regimes, patients co-pay a fraction of the difference between pharmacy retail price of the drug and a reference price. Reference prices are either externally (based on drug prices in other countries) or internally (based on domestic drug prices) determined. In a recent study, we analysed the effects of a change from external to internal reference pricing in Denmark in 2005, finding that the reform led to substantial reductions in prices, producer revenues, and expenditures for patients and the health insurance system. We also estimated an increase in consumer welfare but the size effect depends on whether or not perceived quality differences between branded and other drugs are taken into account.