A cross-sectional study to determine the prevalence of Human Immunodeficiency Virus (HIV) and HIV-associated risk behavior was conducted in February 1998 among 6,324 drug users in 26 drug rehabilitation centres in Malaysia. The majority of respondents were males (97.3%) and Malays (77.8%), administered drugs intravenously (64.6%) and of these 65.4% shared needles. About 78.1% had sexual exposure, of which 55.1% had sex with girl friends, 31.3% with prostitutes and 4.6% with male partners. The HIV prevalence rate in the group was 12.1% and significantly high among injecting drug users (IDU); those sharing needles; those who started addiction at a young age (10-15 years); those who had sexual exposures and had sex with prostitutes.