Drug use is a major mode of HIV transmission in Thailand. This study determined HIV
incidence rates among drug users in a regional drug treatment centre in northern Thailand. A
retrospective cohort of repeatedly-hospitalized drug users between 1993 and 1997 was formed
and HIV incidence rates were calculated. The overall incidence was 11·44 per 100 person-years
of observation. Gender, age, religion, ethnicity, education, employment, income, reasons for
drug use, type of drugs, mode of use, spending on drugs, and referral for treatment are
associated with HIV incidence. However, there are no associations between HIV incidence and
history of treatment and mode of discharge from the centre. This implies that current
treatment modality has no impact on HIV infection risk and other therapeutic approaches
should be explored.