This study attempts to provide real-world evidence of the economic value of lamotrigine as a mood stabilizer for patients with bipolar disorder. Researchers examined longitudinal administrative claims data obtained for patients with a diagnosis of affective disorder between 1997 and 2001. The study compared outcomes for the 12 months preceding initiation of lamotrigine with the 12 months following initiation of lamotrigine in patients previously treated with lithium, carbamazepine or valproic acid, other anticonvulsants, selective serotonin-reuptake inhibitors, or other antidepressants. Outcomes were analyzed using logistic and Tobit regression models. The data suggest that initiation of lamotrigine is associated with reductions in hospital days, a reduction in hospital days of greater than 17 days for some patients, and net cost savings of more than $400 per patient per year.