Prescribing, dispensing, availability and affordability of drugs were evaluated in 100 primary health care centres in 5 provinces of the Islamic Republic of Iran using WHO indicators. On average, 92% of the 12 essential drugs monitored were available in the health centre pharmacies and 95% of the drugs prescribed by the physician were dispensed by the health centre pharmacy. The stock-out duration was less than 1 month on average. A complete treatment for pneumonia cost only 2% of the lowest weekly government salary. The national average number of drugs perprescription was 3.4. Prescription of antibiotics and injectable drugs was very high (58% and 41% respectively). Although availability and affordability of essential drugs is good in this country, rational use of drugs needs to be emphasized.