Treatment of bipolar disorder is complicated by the multiple phases of the illness, dimensional symptomatology that varies considerably across individuals, and a limited spectrum of activity for all mood stabilizers. Randomized, blinded, placebo-controlled studies provide clear guidelines to the overall efficacy of treatments for mania. However, for secondary questions, such as the treatment to employ when lithium or valproate is inadequate as monotherapy, evidence is incomplete, and usually derived from both smaller and less well-designed studies. For mania, the spectrum of efficacy of valproate is broader than for other mood stabilizers. However, many patients obtain inadequate benefit from monotherapy regimens of all mood stabilizers. Recent studies indicate that for patients who develop mania while taking a mood stabilizer, combinations of an antipsychotic and a mood stabilizer yield greater improvement than does continuation of the mood stabilizer alone. Maintenance-treatment studies support the efficacy of lithium, valproate and lamotrigine, although with a different spectrum of benefits and limitations for each. Valproate and lithium provide greater benefits for prevention of manic relapses and control of manic symptomatology than for depression. Several studies indicate actual worsening in depressive aspects of bipolar disorder with lithium treatment. Lamotrigine appears effective in delaying relapse into a new episode, with most benefits limited to delaying time to depression. Lamotrigine has not shown anti-manic activity in placebo-controlled studies. In contrast to traditional antidepressant medications, lamotrigine has not been associated with induction of mania, or of rapid-cycling illness symptomatology. Recent studies reported that carbamazepine was inferior to valproate in acute mania, and inferior to lithium in maintenance treatment. Other putative mood stabilizers have to date yielded negative or inconclusive results in studies in mania. Systematic studies are needed to clarify treatment guidelines for youth with bipolar disorder, and for other special populations, e.g. pregnant women and the elderly.