Introduction. The purpose of this retrospective cohort study was to examine patterns of use of an electronic personal health record among adults diagnosed with diabetes, hypertension or hyperlipidemia. Intermediate behavioral measures (medication possession ratios) and physiological measures of metabolic control for diabetes (hemoglobinA1c), hypertension (blood pressure) and hyperlipidemia (low density lipoprotein) were examined. Methods. Administrative data from Kaiser Permanente Georgia were analyzed. Adult members of with selected chronic diseases of diabetes, hypertension or hyperlipidemia who used the Kaiser Permanente electronic personal health record (KP.Org) during calendar year 2008 were included (n = 9504). The cohort was assessed for a period of 6 months prior to initial KP.Org logon to establish baseline information, and was followed forward in time for a period of up to 14 months to establish post-exposure outcomes. Logon to KP.Org was measured as a frequency tabulation using quartiles of use calculated via univariate analysis. Quartile 1 was set as the lowest frequency of use and served as the referent group. Use functions within KP.Org included secure messaging, encounter details, lab results, medical advice and medications. Intermediate behavioral measures of adherence, medication possession ratios, were calculated by taking the total days of supply of medications dispensed, divided by the total number of days between the first and last prescription refill. Physiological clinical outcome measures included hemoglobinA1c, blood pressure and low density lipoprotein. Logistic and multiple regression analyses were conducted controlling for the covariates of age, gender, percent African American and Geostrata quartile (a proxy measure of socioeconomic status). Results. There was a statistically significant association between highest logon to KP.Org and medication possession ratios among participants stratified by diabetes (p less than 0.0001), hypertension (0.0076) and hyperlipidemia (0.0002). There was a statistically significant association between increased use of KP.Org primary outcome variables of HbA1c (p less than 0.0001), blood pressure (p less than 0.0001) and low density lipoprotein (p less than 0.0001). Conclusion. Increased use of KP.Org was associated with improvements in physiological outcome measures and with medication possession ratios. Medication possession ratios were a significant indicator of improved outcome measures among diabetics and hyperlipidemics, but not among hypertensives. [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.]