Bipolar disorder is characterized by persistent and/or recurrent mood changes between depressive and manic poles. Rapid cycling is a frequent, although underrecognized, condition in bipolar disorder, and it is known to worsen the prognosis of the disease. With regard to the treatment of bipolar depression, there is a shortage of evidence-supported treatment choices, and the literature on the subject includes few references to cases of manic switch induced by lamotrigine.The authors describe a case of a rapid cycling bipolar patient who presented manic symptoms after initiating treatment with lamotrigine.