Thirty pediatric subjects with established type 1 diabetes mellitus will be asked to wear a CGMS for 3 days. During this time the participants will be required to test and record self-monitored blood glucose readings at designated time periods and if they have symptoms of hypoglycemia. The comparison of these values with each other and with different previously defined values of NH will allow for a clear definition of NH to be made. A survey has also been designed to assess participant satisfaction with the CGMS.