The WHO Model List of Essential Medicines has been updated every two years since 1977. The current version, the 13th list, dates from April 2003. It contains 316 active substances which include 12 ARVs and over 60 other essential medicines. This report details the proceedings of the open session and the recommendations of the committee. It includes in annex the 12th WHO model list of essential medicines. Essential medicines are perhaps the most cost-effective element of public health after immunizations and key health promotion habits such as regular exercise. Safe, effective medicines of good quality that are appropriately used already save millions of lives each year and prevent untold suffering. Much has been achieved in the 25 years since the first WHO model list of essential medicines was drawn up.