OBJECTIVE: To assess the effects of web-based care management on glucose and blood pressure control over 12 months in patients with poorly controlled diabetes. RESEARCH DESIGN AND METHODS: For this study, 104 patients with diabetes and HbA(1c) (A1C) > or =9.0% who received their care at a Department of Veterans Affairs medical center were recruited. All participants completed a diabetes education class and were randomized to continue with their usual care (n = 52) or receive web-based care management (n = 52). The web-based group received a notebook computer, glucose and blood pressure monitoring devices, and access to a care management website. The website provided educational modules, accepted uploads from monitoring devices, and had an internal messaging system for patients to communicate with the care manager. RESULTS: Participants receiving web-based care management had lower A1C over 12 months (P < 0.05) when compared with education and usual care. Persistent website users had greater improvement in A1C when compared with intermittent users (-1.9 vs. -1.2%; P = 0.051) or education and usual care (-1.4%; P < 0.05). A larger number of website data uploads was associated with a larger decline in A1C (highest tertile -2.1%, lowest tertile -1.0%; P < 0.02). Hypertensive participants in the web-based group had a greater reduction in systolic blood pressure (P < 0.01). HDL cholesterol rose and triglycerides fell in the web-based group (P < 0.05). CONCLUSIONS: Web-based care management may be a useful adjunct in the care of patients with poorly controlled diabetes.