['To determine whether subgroups of type 1 diabetic patients with different glucose variability indices respond differently to continuous subcutaneous insulin infusion (CSII) in terms of reduced hypoglycemic events.', 'We studied 50 adults with long-standing type 1 diabetes switched to CSII because of persistently high A1C or frequent hypoglycemia despite well-managed intensive basal-bolus therapy. We compared A1C, hypoglycemic events, and glucose variability from self-monitoring of blood glucose profiles at baseline and after 6 months of CSII. Regression analysis was performed to identify predictors of response.', 'In multivariate analysis, baseline low blood glucose index (LBGI) was the best independent predictor of hypoglycemia outcome on CSII (R(2) = 0.195, P = 0.0013). An ROC curve analysis demonstrated a sensitivity of 70.8% (95% CI 48.9-87.4) and specificity of 73.1% (52.2-88.4) by using the LBGI cutoff of 3.34 as predictor of reduction of hypoglycemia on CSII. By grouping patients by LBGI tertiles, we found a 23.3% reduction in hypoglycemic events (<60 mg/dL [3.3 mmol/L]) in the third tertile (range 4.18-9.34) without change in A1C (P < 0.05). Conversely, the first tertile (range 0.62-2.05) demonstrated the greatest A1C reduction, -0.99% (P = 0.00001), but with increasing hypoglycemia.'] Is glucose variability assessed by low blood glucose index predictive of hypoglycemic events in patients with type 1 diabetes switched to pump therapy?