Inclusion Criteria:

• Male and female 7 to 17 years, 11 months at time of first dose
• Must meet DSM-IV diagnostic criteria for Bipolar I (mania, mixed mania) without psychotic symptoms and diagnosed by a psychiatrist
• Parent or Legal guardian must sign informed consent and youth must sign assent
• Must score ≥20 on YMRS at screening and baseline
• Subject may have co-morbid conditions
• If female is sexually active and capable of pregnancy, subject must use an acceptable method of contraception for at least 1 month prior to study entry and agrees to continue with contraception during the study. If female subject is abstinent, she must agree to stay abstinent or use acceptable contraception if sexual activity commences
• Must have negative β-human chorionic gonadotrophin hormone pregnancy test at screening and baseline
• Subjects with a history of substance abuse must agree to continue to abstain from drugs during the trial and have negative drug screen at screening and prior to baseline
• Subject is willing and clinically able to washout of exclusion medicines during screening and prior to administration of lithium
• ECG and blood work must show no clinically significant abnormalities

Exclusion Criteria:

• Subject who are clinically stable on current medication regimen for bipolar disorder
• A current or lifetime diagnosis of Schizophrenia or Schizoaffective Disorder, a Pervasive Developmental Disorder (ASQ score > 15), Anorexia Nervosa, Bulimia Nervosa, or Obsessive-Compulsive Disorder
• Current DSM-IV diagnosis of Substance Dependence
• Positive drug screen at screening and on retest 1-3 weeks later
• Subjects with symptoms of mania that may be attributable to a general medical condition, or secondary to use of medications (e.g. corticosteroids)
• Evidence of any serious and/or unstable neurological illness for which treatment under the auspices of this study would be contra-indicated
• Any serious, unstable medical illness or clinically significant abnormal laboratory assessments that would adversely impact the scientific interpretability or unduly increase the risks of the protocol
• Current general medical condition including neurological disease, diabetes mellitus, thyroid dysfunction, or renal dysfunction that might be affected adversely by lithium, could influence the efficacy or safety of lithium, or would complicate interpretation of study results
• Evidence of current serious homicidal/suicidal ideation such that in the treating physician's opinion it would not be appropriately safe for the subject to participate in this study
• Evidence of current active hallucinations and delusions such that in the treating physician's opinion it would not be appropriately safe for the subject to participate in this study
• Concomitant prescription of over-the-counter medication or nutritional supplements that would interact with lithium or the subject's physical or mental status
• Any use of psychotropic agents other than stimulants within the preceding 2 weeks, including antipsychotics, monoamine oxidase inhibitors, antidepressants; use of stimulants within the preceding week; or fluoxetine or depot antipsychotics in the past month
• Concurrent psychotherapy treatments provided outside the study initiated within 4 weeks prior to screening
• Previous adequate trial with lithium (at least 4 weeks with lithium serum levels between 0.8-1.2 mEq/L)
• History of allergy to lithium
• Psychiatric hospitalization within 1 month of screening for psychosis or serious homicidal/serious suicidal ideation
• Clinician's judgment that subject is not likely to be able to complete the study as an outpatient due to psychiatric reasons
• History of lithium intolerance
• Females who are currently pregnant or lactating
• Sexually active females, who in the investigator's opinion are not using an adequate form of birth control
• Subjects who are unable to swallow the study medication
• Subjects for whom a baseline YMRS score of < 20 is anticipated
• Subjects with an IQ less than 70 (determined using the Wechsler Abbreviated Scales of Intelligence {WASI} Vocabulary and Matrix Reasoning Subscales)