The relative importance of factors which influence order of injecting with a shared needle and syringe

Injecting drug users (IDUs) in Adelaide, South Australia, rated the likelihood of first use of a shared needle and syringe by persons who have characteristics which have previously been suggested as influencing order of injecting. This enabled the relative importance of these factors to be assessed. It was found that those who supply their own drug and injecting equipment have the greatest likelihood of using first, but it is also somewhat advantageous if one is able to promote one's needs, has recently been tested for HIV or is at home when the opportunity to inject arises. Older IDUs and regular users may be slightly advantaged, as may those who inject others and those who were denied first use the last time sharing occurred. A model for predicting order of use is proposed.