OBJECTIVE To report 2 cases of bipolar disorder with recent depression in remission with prominent residual hypersomnia, responding well to the addition of the psychostimulant modafinil. METHODS Two patients with bipolar disorder with recent depressive episodes in remission are presented. Despite the absence of prominent depressive symptoms, both patients had significant hypersomnia, with scores ranging from 15 to 20 (maximum 24) on the Epworth Sleepiness Scale. The addition of modafinil to their medication regimen resulted in a decrease in hypersomnia and improvement in their level of functioning. CONCLUSIONS This is the first report (MEDLINE search, October 7, 2003) demonstrating the use of modafinil in the treatment of hypersomnia in bipolar disorder while mood symptoms were in remission. Hypersomnia frequently occurs in depressive episodes and can be disabling when severe. The patients had optimal mood stabilization with mood stabilizers and antidepressants, but continued to experience excessive daytime sleepiness. Conventional stimulants were not considered because of the risk of triggering mania. The addition of the selective psychostimulant modafinil resulted in significant improvement in the hypersomnia, with improvement in functioning. No adverse effects or mood changes were noted. CONCLUSIONS Modafinil may be a well-tolerated and effective alternative to conventional stimulants in the treatment of hypersomnia, especially in bipolar disorder, where there is considerable risk of switch to mania with stimulant medications. Modafinil may be useful even when depressive symptoms are not prominent.