The Juvenile Diabetes Research Foundation Glucose Sensor Study group is carrying out a large, randomized clinical trial to assess the efficacy, safety and cost-effectiveness of use of real-time continuous glucose monitors (RT-CGM) as an adjunct to standard meter plasma glucose testing. Although the primary outcome in the >= 7.0% cohort is differences in A1c levels, important secondary outcomes are differences in the percent of glucose sensor values either above or below the target glucose range of 70-180 mg/dl and differences in glucose variability. Prevention of biochemical hypoglycemia is a particularly important outcome in the low HbA1c cohort. Since CGM systems measure interstitial rather than plasma glucose and CGM values differ from simultaneous plasma glucose values by up to 18%, it would be extremely useful for comparative purposes to establish a reference range of sensor values in healthy, non-diabetic control subjects for this study and other future investigations. The objective of this protocol is to establish such reference sensor glucose ranges in each of the 3 devices being utilized in the JDRF study.