Background: The rate of lamotrigine-associated rash in patients with mood disorders has not been well characterized. The objective of this report was to determine rash rates in clinical trials of lamotrigine in DSM-IV unipolar depression or bipolar disorder. Method: A retrospective analysis was conducted of rates of lamotrigine-related rash in 12 multicenter studies, including 1 open study, 7 randomized controlled acute trials, and 4 randomized controlled maintenance trials from 1996 to 2001. Results: A total of 1955 patients were treated with lamotrigine in open-label settings (open-label phases preceding or following randomization and 1 stand-alone open-label study); 1198 patients received lamotrigine in controlled settings, and 1056 patients received placebo. In controlled settings, rates of benign rash were 8.3% and 6.4% in lamotrigine- and placebo-treated patients, respectively. Rates of serious rash were 0% with lamotrigine, 0.1% (N = 1) with placebo, and 0% with comparators. In the open-label setting, the overall rate of rash for lamotrigine was 13.1% (N = 257) and of serious rash, 0.1% (N = 2). One mild case of Stevens-Johnson syndrome not requiring hospitalization occurred in a patient treated with lamotrigine. There were no cases of toxic epidermal necrolysis in any setting. Conclusion: Serious drug eruptions associated with lamotrigine were rare. Although rash is a potentially life-threatening reaction, the risk of serious rash due to lamotrigine should be weighed against more common risks associated with untreated or undertreated bipolar depression.