The authors wish to thank the following individuals for their comments and constructive suggestions in revising this document: Henk Bekedam, WHO, China; Jorge Bermudez, WHO Collaborating Centre for Drug Policies, Rio de Janeiro; Andrew Creese, WHO/EDM; Desmond Johns, Joint United Nations Programme on HIV/AIDS; Joan-Ramon Laporte, WHO Collaborating Centre for Research and Training in Pharmacoepidemiology, Barcelona; Monique Mrazek, WHO Collaborating Centre for Health Economics and Drug Policies, London; Jos Perriens, WHO/HIV; Jonathan D. Quick, WHO/EDM; Siripen Supakankunti, WHO Collaborating Centre for Health Economics, Bangkok; Ellen ‘t Hoen, MSF, Paris.