Abstract
We used baseline outcome efficacy (OE) estimates for human immunodeficiency virus (HIV) risk reduction to predict subsequent risk reduction 6 months hence among 792 injection drug users in a prospective study. Declines in drug use, frequency of injection, and needle sharing were found among those with high OE scores after adjustment for baseline behavior and antecedent factors. No OE effect was found in multivariate analysis for shooting gallery attendance, a risk that substantially declined in this cohort. OE for needle disinfection was associated with reduced drug risk behaviors, but not for improved needle hygiene practices over time. The self-efficacy model is useful in understanding psychological factors in risk reduction among injection drug users.