Lithium is used for long-term prophylaxis and the treatment of acute episodes of bipolar disorder. Because of its narrow therapeutic range, lithium toxicity is not uncommon. We describe a bipolar patient who was treated with lithium lead to chronic ataxia secondary to acute lithium intoxication. A 61 year-old man with a long-standing history of bipolar disorder was treated with 1200 mg lithium daily for ten years. He developed signs of lithium intoxication with clouding of consciousness, loss of appetite, tremor, changes in gait and somnolence. His serum lithium concentration had risen to 2.5 mEq/l and lithium treatment was discontinued. The blood tests and the spinal şuid were normal. In his psychiatric examination, he seemed untidy and older than his age with poor self-care, had little interest to interview with limited eye contact. He was conscious, but not oriented by time and place. His memory and attention was poor. He had irritability and poor judgment. Speed and volume of his speech was increased. In neurological examination ataxia and bilateral dysdiadochokinesia was assigned. On discharge, his cognition improved and the tremor completely resolved. However, cerebellar signs were prominent and the patient was unable to walk without help. The condition improved considerably during the first months but the patient still showed slight signs of cerebellar disorders such as ataxia. The lithium intoxication did not leave any mental after effects. We did not detect any acute pathology in cranial MRI. In conclusion, acute lithium intoxication may cause several neurological manifestations such as tremor, ataxia, dysarthria, seizures and in the more severe cases encephalopathy and coma. Lithium toxicity can also cause electrocardiogram (ECG) changes, renal failure, gastrointestinal symptoms, including nausea, vomiting, diarrhea, bloating, and epigastric pain, neuromuscular manifestations such as peripheral neuropathy or myopathy. These changes are usually reversible. However, few cases of persistent neurological deficits have been reported.