Electronic personal health records (PHRs) enable patients to perform a number of health-related tasks through a web-based portal. However, little is known about the usability of these PHRs. This study investigated the usability of a simulated PHR among 107 adults aged 40 to 85 years. Participants performed 15 common health management tasks including finding an upcoming appointment time, reviewing test results, and managing medication dosages. Task performance was video recorded and analyzed to determine the source of any performance difficulties. Usability data was also captured through questionnaires and post-study interviews. Results indicated that participants had difficulty using hyperlinks within the PHR to find information and difficulty interpreting information in the tables and graphs. However, participants' perceptions of the PHR were positive and they were very receptive to the idea of using PHRs to help them perform a number of health management tasks.