This is a 4-month randomized open-label comparative safety, tolerability, and effectiveness trial of Lithium versus Quetiapine for subjects presenting in any phase of Bipolar who currently require a medication change for their illness. Stratified randomization will reduce bipolar type I , bipolar type II , or sub-threshold imbalance across cells. The enrollment goal is 60 subjects, over 24 months from initial regulatory approval. The primary outcome is the difference between lithium and quetiapine in the time to 'all cause' medication discontinuation.