1. Center for Health Promotion Rerearch and Development, School of Public Health, University of Texas at Houston, PO Box 20186, Houston TX 77225, USA
2. National Centre in Epidemiology and Population Health, Australian National University, GPO Box 4, Canberra ACT 2601, Australia
3. National Drug and Alcohol Research Centre, University of New South Wales, and Alcohol and Drug Service, St Vincents Hospital, Darlinghurst NSW 2010, Australia
4. Mackay Regional Health Authority, Queensland Department of Health, PO Box 4, Mackay QLD 4740, Australia
5. Albion Street (AIDS) Centre, Division of Medicine, Prince of Wales Hospital, 150 Albion Street, Surrey Hills NSW 2010, Australia