The Stevens-Johnson syndrome is a serious mucocutaneous vesiculobullous disease that begins acutely and limits itself generally. It may develop by the use of several routinely used drugs. That's why the physicians who prescribe such drugs may be sued for malpractice. In our case, the Stevens-Johnson syndrome that has developed as a result of Lamotrigine use and become a matter in dispute will be examined from a medicolegal perspective. The patient is a 52-year-old lady who had been followed up in the physician's private practice for four years due to major depression diagnosis. After her latest control, 100 mg lamotrigine has started to be administered at 2 doses a day: in the morning and in the evening. In spite of being called for a control, the patient skips this control, and at the 40th day of administration she applies to hospital complaining about eruption, rash and bulge on her skin. Her drug use is stopped, the antihistamine and steroid treatment is started, and the patient is sent back to home. At the night of the same day, she applies to a university hospital complaining about the same symptoms again. She is diagnosed to have Stevens-Johnson syndrome based on findings such as eruption, rash, bulge, inability to open eyes, and high Ig E. Such manifestations caused by drug hypersensitivity reaction appear before us as malpractice cases in forensic practices. While examining such a drug toxicity manifestation from the malpractice perspective, we think that it is necessary to consider whether the prescribing physician has informed the patient about the side effects, whether he was able to know the reaction manifestation emerging during the treatment process, and whether he has taken the necessary actions for treatment of the emerging manifestation.