Adherence to antiretrovirals is critical for longterm effective therapy with first-line medicines. This important study describes how groups from the International Network for the Rational Use of Drugs in East Africa developed and tested simple facility-based indicators to measure adherence. The report below demonstrates that such measurements can be reliably performed, meaning that adherence defined in different ways can be routinely reported. This work also demonstrates the value of operational field research carried out by national researchers and health workers within a network.