Temporal differences in human immunodeficiency virus (HIV) risk-related behaviors among injection drug users in Rome, Italy, were analyzed in 487 drug users recruited in 1990 and 450 recruited in 1992. Sharing of syringes decreased among self-reported HIV-positive drug users between 1990 and 1992, but there was no change in their sexual behavior. Fewer HIV-seronegative drug users reported passing on used syringes in 1992 than in 1990; however, there was no change in the percentage of seronegative subjects using previously used syringes, and a reduction in condom use with primary partners. There still exists a great potential for transmission of HIV infection among injection drug users and from injection drug users to the general population.