BACKGROUND: Low-threshold primary healthcare (PHC) centres targeting injecting drug users (IDUs) are increasingly being created to offer preventative and opportunistic services. However, no data are available on the characteristics of clients who utilise such services, or the effectiveness of these services in facilitating prevention or treatment. METHOD: A retrospective clinical record audit examined the characteristics, service utilisation patterns and referral uptake of 384 clients presenting to a low-threshold PHC service in Sydney, Australia. RESULTS: Of the 384 clients, 85% were IDUs. Sixty-two percent reported also having access to a general medical practitioner (GP), with this group more likely to report taking benzodiazepines or other psychoactive medication. Despite this relatively high level of GP access, only 50% were fully vaccinated against hepatitis B virus (HBV). Testing for blood-borne viral and sexually transmitted infections were the most common reasons for presentation to the PHC. Most (82%) clients made at least one return visit, with an average of 3.5 presentations per client. All clients were offered HBV vaccination where indicated (n = 145); and more than half (55%) of referrals to external services were attended. Clients accessing this PHC were younger, more likely to be male and born outside Australia than IDUs attending needle syringe programs (NSPs) in Australia's most populous state, New South Wales. CONCLUSION: Results suggest that this low-threshold PHC service was underutilised and its role as a low-threshold healthcare outlet remains limited. Further research is needed to more clearly delineate the health and economic benefits of this model.