Stevens-Johnson syndrome (SJS) and TEN are rare, acute, life-threatening allergic reactions, which affect skin and mucous membranes. Anticonvulsant drug-induced Stevens-Johnson syndrome may occur with the use of anti-epileptic drugs such as phenobarbital, phenytoin, carbamazepine and lamotrigine. This clinical picture usually appears within two months after the beginning of treatment and characterized by life-threatening severe skin reactions. In this paper, a case that developed SJS-TEN in the third week of lamotrigine therapy and her treatment process is presented. A 19-year-old female patient with complaints of unhappiness, loss of appetite, insomnia, decrease in academic performance, difficulty concentrating which has existed for the last 2 months was admitted to our outpatient clinic. On psychiatric examination, her mood was depressive and the affect was sad. In her psychiatric history, it was learned that there were periods of time -up to 20 days- when she was feeling herself a little more energetic, sleep late at night, she had an increase in financial spending and self-care. In the light of available data, the patient was diagnosed as bipolar mood disorder, type 2 (current episode is depressive) according to the DSM-IV diagnostic criteria. She was initiated lamotrigine 25 mg/day therapy. Daily dose of lamotrigine was increased to 75 mg/day by the end of the third week. The patient was admitted to the emergency room on the day 24. On physical examination, there were erythematous maculopapular rash and crusted lesions on face, extremities, trunk and buttocks. Additionally, mucocutaneous ulcerations on the lips and oral mucosa; redness of eyes, eyelids-the conjunctiva edema and visual acuity loss were present. The patient was admitted to the dermatology clinic with the diagnosis of lamotrigine-induced SJS. SJS and TEN are hypersensitivity reactions that may occur due to many drugs and can cause life-threatening skin reactions. TEN is accepted as severe form of the SJN and differential diagnosis is based on according to the afşicted body surface area. If involvement of body surface is under 10% SJS, between 10-30% is SJS-TEN coexistence, while over 30% is considered TEN. In our case, because the entire body surface involvement is close to 30%, it was evaluated as SJS-TEN coexistence. The role of drugs in the etiology of SJS has been reported as 50%. In clinical trials of lamotrigine treatment for bipolar disorder and other mood disorders, when used alone, the incidence of skin reactions is 0.08%. Skin reactions, occurring due to lamotrigine and other antiepileptic drugs, starting from a simple morbilliform rash and urticaria, covers a wide range which could cause serious consequences that may be up die. Initiation of lamotrigine treatment with higher doses or rapid increase of the dose, increase the risk of allergic skin reactions. Mortality rate of SJS and TEN is under 5 %. Mortality usually occurs due to staphylococcus or pseudomonas skin infections or pulmonary sepsis. In SJS cases, age of patient, the involvement of epidermal decomposition in skin lesions and quitting the drug immediately when reaction is observed, are the predictors of prognosis.