Cities central to HIV response for people who use drugs.

Tinasti K Global Health Programme, Graduate Institute of International and Development Studies, Geneva, Switzerland. Electronic address: khalid.tinasti@graduateinstitute.ch.
Audoin B International Association of Providers of AIDS Care, Washington DC, USA.
Jomier B City of Paris, Paris, France.
Delfraissy JF Agence nationale de recherches sur le SIDA et les hépatites virales, Paris, France.
Lévy Y Institut national de la santé et de la recherche médicale, Paris, France.
Barré-Sinoussi F Institut Pasteur, Paris, France.