Over the last decade, personal health records (PHRs) have been increasingly recognized and actively promoted by the U.S. federal government and experts as a tool for improving healthcare and containing skyrocketing costs in the U.S. More recently, the 2010 health reform legislation includes PHRs as an important means to improve the quality and efficiency in healthcare delivery. However, the use of PHRs by various patient groups has not been well studied, and its utility has not been firmly established. We have developed a web-based, patient-centered PHR, named personal health information management system (PHIMS), and evaluated it in multiple locations since 2002. The first version was evaluated at the Bone and Joint Center of the University of Washington (UW). The system was well received by patients, staff and physicians, and it remains in active use to date. To study variability in the use of PHIMS and its acceptance by different populations, we deployed it to the three additional sites: (1) a low-income, elderly housing facility in Everett, WA, (2) UW Regional Heart Center (RHC), and (3) UW Mental Health Clinic (MHC). Our research demonstrated that PHR could be useful in diverse settings. PHIMS was found to be particularly beneficial in improving patient-provider communications and encouraging patients to take an active role in managing their healthcare. For young collegiate adults at the UW MHC, our system helped them recognize potential mental health problems and encouraged them to proactively seek care from professionals. Most of this population did not have any problem utilizing our web-based system. As a result, the system was clinically accepted by the UW MHC, and it is being widely used by students and clinical staff. On the other hand, PHIMS use by the low-income elderly at the EHA was very minimal even with the free availability of high-speed Internet enabled computers and assistance. For the significant majority of the low-income elderly, their lack of computer skills, technophobia, low healthcare literacy, and reduced physical/cognitive abilities contributed to limited PHIMS use. Only a small fraction of this population were self-sufficient enough to be able to use the system by themselves. In spite of this low use at the EHA, we believe that the next-generation elderly would be more technically skilled than the current generation, as more computer-literate individuals age. Thus, a much higher number and percentage of elderly individuals would be able to use PHR and benefit from it in the future. The digital divide refers to the gap between individuals with easy access and effective use of information and communication technology and those with limited or no access and use. This multi-year, multi-site, multi-population study clearly illustrates that the digital divide exists in the use of PHRs among population groups, but it also indicates that the width and depth of the divide is becoming narrower and shallower. Although age-related decreased physical and mental functions among older people may persist as an obstacle in the future, the influence of some dominant factors to the digital divide in the past, such as income, computer literacy and age (in general), would decline or disappear. We also found that lack of motivation becomes an important barrier. Therefore, for widespread adoption and active use of PHRs or PHR applications, motivating individuals by providing incentives and offering compelling functions and features solving their unmet needs (e.g., specialist scheduling at the RHC and MHC and mental health self-assessment at the MHC) would be essential. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]