Depression is much more common in the life course of people with bipolar disorder than mania or mixed states. Unfortunately, few established treatments are available, and new ones are needed. Modafinil is a novel stimulant approved for treating improving wakefulness in patients with excessive sleepiness associated with narcolepsy, obstructive sleep apnea, and shift-work sleep disorder. Given that bipolar depression is commonly associated with fatigue and somnolence, modafinil is a logical choice. In one recent study of moderate size (n = 85), modafinil was shown to be more effective than placebo in treating bipolar depression. The incidence of cycle induction in this trial was very low (lower than placebo), although isolated case reports of mania, hypomania, or mixed states have been reported. Given the limited options for bipolar depression, modafinil should be considered in patients who have not responded to approved treatments, although more research is needed. © Current Medicine Group LLC 2008.