This prospective study of 2960 injection drug users investigated the dynamic nature of HIV behavioral risk factors between 1988 and 1994. Behavioral risks were assessed semi-annually. Robust regression models of time-dependent covariates were used to identify longitudinal predictors of behavior change. Maintenance of risky behaviors varied over time, with risk reduction seen more among HIV infected participants than among HIV seronegatives. Those at highest risk for HIV transmission were least likely to cease engaging in these behaviors. Interventions staged according to risk behaviors, targeting incremental risk reduction rather than only promoting abstinence, may be more successful in reducing HIV transmission among drug injectors.