In injecting drug users (IDU) newly entering drug treatment centres in Berlin, HIV seroprevalence continuously decreased from 1985 through 1992. A recent cross-sectional study with multi-site sampling (n = 472) showed significantly differing HIV prevalences by site of recruitment (treatment centres 6%, storefront units 20%, infectious disease clinic 56%). In multivariate analysis, the borrowing of syringes in prison was the strongest independent predictor of HIV infection. A majority of the IDU have reduced risks of infection. However, current risk behaviour is common. Of all IDU, 48% reported the borrowing of syringes within the previous 6 months, only 13% had consequently used condoms. Current borrowing of syringes was associated with younger age, shorter history of intravenous drug use, negative HIV serostatus, and non-participation in methadone maintenance programmes. Continued preventive efforts against HIV transmission among IDU are needed.