Abstract
Dimensions of HIV infection risks were investigated in 1,245 injecting drug users (IDUs) in Sydney, Australia. Factor analysis of the degree of risk of the 33 items of risk behaviours revealed ten dimensions, which covered the domains of oral sex, withdrawal before ejaculation, protected intercourse, unprotected vaginal intercourse, saliva, blood products, manual sex, needles and syringes, unprotected anal sex, and social transmission. The perceived riskiness of particular activities closely approximated the objectively assessed risk of particular practices. Women assessed the risks of classes of activities (with the exception of oral sex) as being higher than did men. IDUs appear to have readily interpretable and consistent perceptions of HIV transmission risks, and these dimensions have utility for measuring perception and knowledge of HIV transmission risks.