The increasing adoption of Internet and social media have facilitated the emergence of patient opinion leaders (POLs). These influential individuals are living with a chronic disease and are writing about their experiences on Internet blogs and social media websites. Popular and highly-trusted patients are labeled as POLs because their work influences the decision-making of other patients. Top POLs have tens of thousands of followers who subscribe to their websites, blogs, and online social media accounts. POLs usually focus on one therapeutic area and provide disease-related information, treatment options, and emotional support to other patients. Additionally, some POLs are health activists who help shape health policy and provide input into clinical trial design including endpoint development. As healthcare increases its focus to center around the individual patient, pharmaceutical companies and government agencies will seek out POLs for their personal perspectives. A formal methodology to measure the influence and reach of POLs has yet to be established. Their influence on the Internet can be determined by the size of their audience (e.g., Twitter followers), relevancy of posted content to the disease state of interest, frequency of posted content, and perceived trustworthiness based on various scales (e.g., Google’s PageRank algorithm). By characterizing and indexing POLs, interested stakeholders can easily engage with them to incorporate the patient’s voice into clinical trials, market research, health policy, and marketing. As an example, researchers can capture and leverage the large audience of an influential POL to recruit patients for a clinical trial or to garner feedback on the endpoints of a clinical trial from the patients’ perspectives. This paper’s objective is to evaluate the importance of POLs, to propose a method to measure a POL’s influence, and to examine the possible roles of POLs.