Abstract: Objective The study provided an estimation of the number of HIV-infected drug users in Dongguan city. Methods The survey was based on the number of registered drug abusers from the compulsory drug rehabilitation agency of the Public Security Bureau in Dongguan. The population size was estimated through the simplified multiplier and capture-mark-recaptured methods. The number of HIV infected individuals among these drug abusers was calculated in accordance with the surveillance results of the HIV infection rates in relation to drug abusers in Dongguan from 2004 to 2006. Results The population range of drug abusers in Dongguan city was between 34 698 and 49 175, 1.78 to 2.52 times the registration number and 9.61 to 13.63 times the number of drug users in the compulsory drug rehabilitation agency, Dongguan, 2006. The average annual HIV infection rate was 5.12% among drug abusers over the past three years, reported by the compulsory drug rehabilitation agency in Dongguan. An estimated range of the number of HIV infected drug abusers in Dongguan was 1777 to 2518. Conclusion The registration number of local drug abusers or drug abusers in the rehabilitation agency last year multiplied by the reference multiplier, which is determined by the local mobile demographics, the seriousness of drug abuse, anti-drug achievement and other pertinent factors, can serve as an estimation of the population size of local drug abusers, upon which the calculated number of HIV infected individuals among this population is based.