OBJECTIVE - To evaluate differences in HbA1c concentrations between centers and to assess the factors associated with glycemic control in young people with type 1 diabetes in Scotland. RESEARCH DESIGN AND METHOD - Data on 1,755 patients (94% of those registered) were collected from 18 centers providing care to children < 15 years of age. At every clinic visit, a duplicate HbA1c sample was measured in a reference laboratory and clinical information was collected prospectively. RESULTS- Average HbA1c concentration was 9.1% (range 5.0-15.0). The following significant associations with HbA1c level were identified: age, insulin regimen, BMI, season, social circumstances, and family history, HbA1c concentrations were significantly worse in older children (age 10-15 years 9.5% vs. other ages 8.8%, P < 0.001), those using two injections per day (2/day 9.1% vs. 3/day 8.8%, P < 0.01), children without both parents at home (9.4 vs. 9.0%, P < 0.001), a sibling with diabetes (9.7% vs. no family history 9.1%, P < 0.001). HbA1c concentration ranged from 8.1 to 10.2% between centers, after adjustment for factors associated with poor HbA1c (P < 0.001). CONCLUSIONS - The overall glycemic control of diabetic young people in Scotland is equivalent to a Diabetes Control and Complications Trial HbA1c concentration of 8.7%, placing the majority at a high risk of the complications of diabetes in adulthood. Although factors were significantly associated with poor HbA1c, adjustment for these did not explain the differences between centers. We suggest that factors not analyzed in DIABAUD2 (e.g., deployment of resources, organization of the clinical structure, strategies of care, and clinic philosophy) are the determinants of HbA1c. We speculate that the style of utilization of optimum resources is the key to achieving good glycemic control.