The aim of the present study was to identify the psychosocial factors associated with the intention and behavior of not sharing used needles and syringes among 459 intravenous drug users (IDUs). The intention to not share used needles was positively associated with personal normative beliefs and self-efficacy; it was negatively related to the proportion of injections with lending used needles and borrowing syringes from sexual partners. Borrowing used needles was negatively associated with intention whereas loaning syringes was positively related to a negative HIV test result. These results suggest that it is only when a direct personal exposure to HIV infection is possible (borrowing) that intention not to borrow is highlighted. Moreover, being HIV positive appears to reduce loaning used syringes.