Several case reports and open studies have reported the efficacy of lamotrigine in bipolar depression. A randomised placebo-controlled 7-week study comparing two doses of lamotrigine with placebo in 195 patients with moderate to severe bipolar depression has now been completed. Lamotrigine was superior to placebo after 3 weeks as assessed by changes in the Montgomery-Asberg Depression Rating Scale (MADRS). A response, defined as more than 50% improvement on the MADRS occurred in 56 and 48% of the lamotrigine 200 and 50 mg/day groups, respectively, compared with 29% for placebo (P<0.05). There was no evidence that lamotrigine destabilised mood or precipitated mania. Tolerability was good and there were no cases of serious rashes. Preliminary results from an ongoing study also indicate that lamotrigine is more effective than gabapentin in bipolar depression. In conclusion, lamotrigine is effective in alleviating bipolar depression, without causing mood destabilisation. Slow dosage escalation yields good tolerability.