This study evaluated the efficacy and safety of lamotrigine in binge-eating disorder (BED) associated with obesity. Fifty-one outpatients with BED by Diagnostic and Statistical Manual of Mental Disorders, fourth edition criteria, and obesity were randomized to receive either lamotrigine (N=26) or placebo (N=25) in a 16-week, double-blind, flexible-dose study. Lamotrigine (236±150 mg/day) and placebo had similar rates of reduction of weekly frequency of binge-eating episodes and binge days, weight and BMI, measures of eating pathology, obsessive–compulsive symptoms, impulsivity, and global severity of illness. However, lamotrigine was associated with a numerically greater amount of weight loss (1.17 vs. 0.15 kg) and significant reductions in fasting levels of glucose, insulin, and triglycerides. It was also well tolerated and associated with no serious adverse events. As a result of an exceptionally high placebo response, it is likely that for efficacy measures except for body weight and metabolic indices, the study was incapable of detecting potentially clinically important drug–placebo difference.