Injection drug users (IDUs) are at high risk of acquiring hepatitis C virus (HCV) infection, and co-infection with human immunodeficiency virus (HIV) and HCV is highly prevalent among this population. Yet few are evaluated and treated for HCV. Low levels of awareness and knowledge about HCV represent a significant challenge to prevention and treatment among IDUs. HCV education is associated with increased disease- specific knowledge, interest in and willingness to accept treatment, and increased liver clinic attendance. The Internet offers the opportunity to deliver HCV prevention and treatment information to IDUs in a convenient and timely fashion. However, little data is available about the use and impact of Internet and mobile phone-based interventions to disseminate health interventions for IDUs. This study will conduct a formative evaluation and will design and evaluate the feasibility and acceptability of a theory-guided mobile website to disseminate HCV and HIV health information. The website is intended to complement drug abuse treatment services by offering educational support services including information about HCV and HIV, incorporating a personal HCV risk assessment, and integrating a search feature to enable users to locate HCV and HIV health care providers. Increasing knowledge and awareness of HCV among at-risk populations is consistent with the national strategy for prevention and control of HCV. Aims for the first phase (N = 200) are: (1) To characterize access to and the use of mobile phone technology and Internet activity among methadone maintenance treatment (MMT) patients; (2) To measure attitudes regarding the use of digital modalities (text messaging, e-mail, and Internet) to receive health information including HCV and HIV prevention, testing, and treatment information among MMT patients; and (3) To identify predictors of access to and the use of mobile technology and the Internet for health or medical purposes among MMT patients. Based on results obtained in the first phase, the aims for the second phase are: (1) To design and refine a mobile optimized website for the dissemination of HCV and HIV prevention, testing, and treatment information with input from digital technology experts and feedback from MMT patients; and (2) To conduct a randomized pilot study to determine whether tailored motivational text messages will increase the use of the mobile website among MMT patients. We will randomly assign 40 MMT patients who own a mobile phone to one of two conditions: 1) tailored motivational text messages; or 2) no text messages. Assessments will occur at study entry and 30 days post-randomization. We hypothesize that participants randomized to the tailored motivational text message condition will have significantly increased knowledge of HCV, a higher frequency of repeat visits to the website, and will be more likely to complete a personal HCV risk assessment survey and to be tested for HCV at the 30-day follow up than those who do not receive tailored motivational text messages. If feasible and acceptable, the website will provide reliable, efficient, and high-quality HCV health information targeting drug users with the potential for wide dissemination.