Prior research indicates that injection drug users forget substantial proportions of their injection partners when asked to recall them. Such under-reporting hampers both ascertainment of the injection networks that underlie transmission of blood-borne pathogens and contact-tracing efforts for disease control. We report here an evaluation of supplementary elicitation techniques – a set of prompting strategies and recall cues – employed in a study that involved tracing of injection partners. Sixty-one index drug injectors in Seattle participated in the study. The supplementary partner elicitation techniques enhanced recall of injection partners substantially and identified persons relevant to transmission of blood-borne pathogens. As a set, the supplementary techniques elicited additional partners from 70% of injectors, and the additional partners elicited represent a 75% increase on average. Drug injectors who recalled many partners before administration of the supplementary techniques tended to report more additional partners in response to the supplementary techniques than injectors who freely recalled few partners. In addition, partners elicited by the supplementary techniques were as likely as freely recalled partners to test positive for hepatitis C virus antibody and engage in risk behaviour with indexes. Furthermore, we found that the supplementary techniques boosted connectivity in the observed injection network considerably.