Telemedicine is one approach to managing patients with chronic illness. Several telephone-based monitoring studies of diabetes patients have shown improved glycosylated hemoglobin (HbA1c), blood pressure (BP), and low-density lipoprotein (LDL) levels. The purpose of this study was to evaluate an investigational in-home telemetry device for improving glucose and BP control over 6 months for patients with type 2 diabetes. The device was used to transmit weekly blood glucose, weight, and BP readings to a diabetes care manager. We conducted a two-arm, parallel-comparison, single-blind, randomized controlled trial among Kaiser Permanente Northern California members 18-75 years old with type 2 diabetes mellitus and entry HbA1c levels between 7.5% and 10.0%. Participants were randomly assigned to either the telemonitoring arm or the usual care arm. We observed very small, nonsignificant changes in fructosamine (telemonitoring, -54.9 ?mol; usual care, -59.4 ?mol) and systolic BP (telemonitoring, -6.3 mm Hg; usual care, -3.2 mm Hg) from baseline to 6 weeks in both groups. At 6 months, we observed no significant intergroup differences in change from baseline for HbA1c, fructosamine, or self-efficacy. However, LDL cholesterol in the telemonitoring arm decreased more than in the usual care arm (-17.1 mg/dL versus -5.4 mg/dL; P=0.045). Although HbA1c improved significantly over 6 months in both groups, the difference in improvement between the groups was not significant. This lack of significance may be due to the relatively healthy status of the volunteers in our study and to the high level of care provided by the care managers in the Santa Rosa, CA clinic. Further study in subgroups of less healthy diabetes patients is recommended.