About the Study: This research study is being conducted to see if diabetic ketoacidosis has any impact on learning, behavior and development in children with Type 1 diabetes mellitus. If there is an impact, is it transient or persistent? Sixty to 80 children between the ages of 4 to 17 years with Type 1 diabetes mellitus will have neuropsychological testing and a non-sedated MRI scan of the head performed. The investigators will compare this to a control group of 30-40 children between the ages of 4 to 17 years without Type 1 diabetes mellitus. The children with Type 1 diabetes mellitus will not have any changes made to their current diabetes regimen. The children with Type 1 diabetes mellitus should continue to check blood glucose values as required by your doctor and bring their meter(s) for downloading to each visit. The children with Type 1 diabetes mellitus should also tell your doctor about the frequency of severe low and high blood glucose values.

Participant Schedule:

1. One visit for 3-4 hours at the Stanford Medical Center to complete neuropsychological testing and to become familiar with the MRI scanner.
2. Subjects who need to become more familiar with the MRI scanning process will view a video tape at home.
3. One visit for 1-2 hours at Stanford Medical Center to have the MRI scan of the head completed.
4. Subjects between 10 and 17 years of age will also be asked to complete two additional abbreviated neuropsychological tests at one week and one month from enrollment.
5. Subjects may have the complete neuropsychological testing and MRI scan repeated 15 months from time of enrollment.

Inclusion Criteria:

To take part in the study, the participant must meet the following inclusion criteria:

1. Be between the ages of 4 to 17 years.
2. Either has been diagnosed with type 1 diabetes mellitus OR does not have type 1 diabetes mellitus

Exclusion Criteria:

If the interested participant has a history of head trauma with any loss of consciousness, prematurity (born less than 30 weeks of gestation), significant developmental delay (lack of single word speech or ability to walk independently by 18 months of age), neurologic disease independent of diabetes (eg seizure disorder or medical contraindication to MRI procedure (eg metal appliances such as braces).

Sixty to 80 children between the ages of 4 to 17 years with Type 1 diabetes mellitus will have neuropsychological testing and a non-sedated MRI scan of the head performed. We will compare this to a control group of 30-40 children between the ages of 4 to 17 years without Type 1 diabetes mellitus.