We will determine the HCV infection status of potential study subjects within a cohort of 2,000 IDUs receiving care in our centres (Appendix 1). For those who carry HCV antibodies (expected n = 1800), a test for HCV viremia and genotype will be performed. By these evaluations, we expect up to 600 individuals to be viremic and carry HCV genotype 2 or 3. Within this group, 200 consecutive patients (100/study strategy) will receive therapy for HCV, based on their eligibility to do so according to Provincial guidelines for the reimbursement of medications. Patient allocation will be according to the study site where they regularly receive care. At two sites, patients will be enrolled in a DOT program with on-site full-time nursing and counseling support (high intensity, 50 patients/site). At the other two sites, patients will receive medication on a weekly basis and will have access to part-time nursing and counseling support (low intensity, 50 patients/site). Medical follow-up will be according to current clinical standards, and the primary endpoint of the study will be the rate of sustained virologic response (SVR) six months after completion of treatment. Within the study described above, we will use standardized methodologies to calculate the total health care costs related to the treatment of HCV infection. We will also assess the effect of treatment on the quality of life (QoL) of study participants.