The purpose of this study is to use magnetic resonance imaging (MRI) to examine brain structure, function and chemistry in people with bipolar disorder who are being treated with either quetiapine or lithium. Both of these medicines are FDA-approved to treat mania in adults and lithium is also FDA approved in children; quetiapine is commonly used in children with mania, but is not FDA approved for this indication in this age group.

Inclusion Criteria - First-episode manic bipolar patients (N=100; 15-20 patients/year):

1. Patients meet DSM-IV criteria for type I bipolar disorder, manic or mixed.
2. Patients have an index Young Mania Rating Scale (YMRS)70 total score >20.
3. Patients have <3 months of lifetime anti-manic or anti-depressant medication exposure, including no active psychotropic medication in the one weeks prior to the index admission. Importantly, patients will NOT be taken off medications for this study; this criterion is to exclude subjects receiving active treatment at the time of admission to support the 'first-episode' criterion.
4. Patients have no more than two prior episodes of major depression.
5. Patients are between 12 and 35 years old; subjects < 18 yrs old have a Tanner greater than or equal to 4

Exclusion criteria: All subjects will be excluded from participation for the following reasons.

1. Any chemical use disorder within 3 months.
2. Any medical or neurological disorder that could influence fMRI and MRS results.
3. A history of mental retardation or an estimated IQ total score <85.
4. An MRI scan is contraindicated in the subject.
5. The patient cannot attend follow-up visits.
6. A positive urine pregnancy test (in women).

You are being asked to take part in this research study because you have been diagnosed with bipolar disorder and are currently experiencing mania. Mania is identified by periods of extreme elation or irritability, excessive energy, racing thoughts, difficulty sleeping, poor judgment and/or reckless behavior. Bipolar disorder is an illness in which people experience mania as well as mood swings into depression. To participate in this study you must be at least 12 years old and no older than 35.