Treatment for hepatitis C virus (HCV) is rarely received by injection drug users (IDU), particularly those co-infected with HIV. We propose a framework for understanding factors that affect utilization and adherence to HCV therapy among HCV mono-infected and HIV/HCV-co-infected IDU. Provision of treatment requires calculation of risks and benefits including evaluation of a number of time-varying factors that collectively determine a gradient of treatment eligibility, advisability and acceptability, the relative importance of which may differ in co-infected and mono-infected IDU. Treatment eligibility is determined by a number of non-modifiable and modifiable contraindications, the latter of which can change over time rendering patients who were once ineligible eligible. Among those eligible, treatment need can be assessed by liver biopsy and therapy may be deferred in those with no liver disease and started in those with significant liver disease. Among those with moderate disease, further consideration of treatment advisability (medical factors that affect treatment response) and acceptability (individual, provider and environmental barriers) is needed before treatment decisions are made. These factors are dynamic and thus should be continually evaluated even among those who may not initially appear to be ready for treatment. An evaluation of this framework is needed to determine applicability and feasibility. Until then, treatment decisions should be made on an individual basis after careful consideration of these issues by provider and patient and efforts to develop novel strategies for identifying IDU who need treatment most (alternatives to liver biopsy) and multidimensional approaches to deliver treatment for HCV while addressing other factors including HIV infection, depression and drug use should be continued.