The authors investigated use of the internet-based patient portal, kp.org, among a well-characterized population of adults with diabetes in Northern California. Among 14,102 diverse patients, 5671 (40%) requested a password for the patient portal. Of these, 4311 (76%) activated their accounts, and 3922 (69%), logged on to the patient portal one or more times; 2990 (53%) participants viewed laboratory results, 2132 (38%) requested medication refills, 2093 (37%) sent email messages, and 835 (15%) made medical appointments. After adjustment for age, gender, race/ethnicity, immigration status, educational attainment, and employment status, compared to non-Hispanic Caucasians, African-Americans and Latinos had higher odds of never logging on (OR 2.6 (2.3 to 2.9); OR 2.3 (1.9 to 2.6)), as did those without an educational degree (OR compared to college graduates, 2.3 (1.9 to 2.7)). Those most at risk for poor diabetes outcomes may fall further behind as health systems increasingly rely on the internet and limit current modes of access and communication.