Objective: To determine the effectiveness of a provider-based education and implementation intervention for improving diabetes control. Design: Cluster-randomized trial with baseline and follow-up cross sections of diabetes patients in each participating physician's practice. Setting: Eleven US Southeastern states, 2006-08. Participants: Two hundred and five rural primary care physicians. Intervention: Multi-component interactive intervention including Web-based continuing medical education, performance feedback and quality improvement tools. Primary Outcome Measures: 'Acceptable control' [hemoglobin A1c ≤9%, blood pressure (BP),140/90 mmHg, lowdensity lipoprotein cholesterol (LDL),130 mg/dl] and 'optimal control' (A1c,7%, BP,130/80 mmHg, LDL,100 mg/dl). Results: Of 364 physicians attempting to register, 205 were randomized to the intervention (n = 102) or control arms (n = 103). Baseline and follow-up data were provided by 95 physicians (2127 patients). The proportion of patients with A1c ≤9% was similar at baseline and follow-up in both the control [adjusted odds ratio (AOR): 0.94; 95% confidence interval (CI): 0.61, 1.47] and intervention arms [AOR: 1.16 (95% CI: 0.80, 1.69)]; BP,140/90 mmHg and LDL,130 mg/dl were also similar at both measurement points (P = 0.66, P = 0.46; respectively). We observed no significant effect on diabetes control attributable to the intervention for any of the primary outcome measures. Intervention physicians engaged with the Website over a median of 64.7 weeks [interquartile range (IQR): 45.4-81.8) for a median total of 37 min (IQR: 16-66). Conclusions: A wide-reach, low-intensity, Web-based interactive multi-component intervention did not improve control of glucose, BP or lipids for patients with diabetes of physicians practicing in the rural Southeastern US. Published by Oxford University Press in association with the International Society for Quality in Health Care 2011.