Wernicke-Korsakoff syndrome is one of the neurological complications that occur due to thiamine deficiency. Wernicke encephalopathy is an acute or sub-acute encephalopathy, which may be seen after chronic malnutrition situations such as long-term alcohol usage, hunger strike, hyperemesis gravidarum and gastrointestinal surgery. Wernicke Encephalopathy’s classical triad is ataxia, eye movement abnormalities and confusion or memory impairment. While it can be totally cured if it is treated at early stage, skipped cases may lead to Korsakoff Syndrome, which is a subacute/chronic dementia caused by thiamine deficiency. Our case is a 40-years-old male. 25 years of regular alcohol consumption, especially in increased amount in last 2 years, presented with forgetfulness, walking difficulties and falling, forgetting the time and places, telling events that do not happened. Seen in the examination chair, the patient’s consciousness state was good and cooperation was partial. He was uninterested in examiners questions. His time and place orientation was impaired. His mood was depressive, affect was restricted. His associations were slowed down and goal directed. In his neurological examination, there was inability of looking up. There was weakness and atrophy in the distal muscles of the patient, who could not walk without help. Reşexes were hyperactive in lower extremities. Dysdiadochokinesia was present. In his detailed history, it was founded that he was not leaving his house for 1 year. Nine months ago signs such as forgetfulness, forgetting where he put his belongings, repeating the same questions had begun. In last three months, in addition to latter signs, walking difficulty, falling and double vision signs had started. His relatives reported complaints such as forgetfulness, loosing belongings, telling the same things repeatedly especially in the last two months. Mixing up time and days, speaking meaninglessly, difficulty in focusing and telling stories of activities that he had never done complaints were also reported. There weren’t any pathological findings in routine biochemistry, hemogram, thyroid function tests, serologic tests and PA lung graph. Anti TPO, anti TG, RF, CRP, vit-E, vit-B, HLA-B27, ANA, ANCA, GH, ACTH, LH, FSH, PRL and cortisol blood levels, which were measured in order to evaluate dementia etiology, were in normal range. Cranial MRI and EEG finding were normal. EMG was normal. In neuropsychological tests, there was visio-spatial function impairment accompanied with moderate-severe memory dysfunction. Memory was impaired in encoding, storage and retrieving phases. The patient was diagnosed with Wernicke-Korsakoff Syndrome and treated with diazepam detoxification therapy. In the 5th day of the IV thiamine replacement therapy, patient’s ataxia and eye symptoms were improved. The patient whose symptoms, except memory symptoms, cured was discharged from hospital in 6th week of his treatment. Parenteral thiamin treatment should be given rapidly in order to avoid Korsakoff Syndrome or death, in cases that gives findings of Wernicke Encephalopathy. Ataxia is usually starts recovering in the early weeks; but it may take 1-2 months or more time to recovery. Residual nystagmus and ataxia may be present with some of the patients.