Lithium therapy can induce acute toxic reactions especially during overdosage. Exceptionally, permanent neurologic sequelae persist after the acute toxic reaction. These sequelae are more often cerebellar symptoms. Dementia, parkinsonian syndromes, choreoathetosis, brain stem syndromes and peripheral neuropathies have also been described. They are defined as irreversible if they persist more than two months after the interruption of lithium treatment. These neurologic complications occur frequently after voluntary or accidental poisoning but they may be observed even if the serum lithium dosage is below toxic level. Risk factors other than overdose are not well identified. Neurologic lesions induced by lithium can occur in the first days of the treatment as well as after years of maintenance therapy. Age and psychiatric diagnosis do not seem to be correlated with an increased risk of lithium induced neurotoxicity. Sex may be a risk factor, because of an overrepresentation of women among the case reports. The lithium-neuroleptic combination is another possible (although controversial) risk factor precipitating the occurrence of irreversible neurologic sequelae. Haloperidol was first implicated, but it has been shown that others neuroleptics, in combination with lithium, can induce similar toxic reactions. Intercurrent somatic illness with pyrexia often precedes the acute toxic reaction, and special attention must be paid to patients treated by lithium when they become hyperthermic. Major surgery, concurrent treatment with diuretics, renal failure, low food intake or low-salt diet are more uncommon precipitating factors. Available pharmacological treatments have not yet proved to be helpful. Even when the lesions are irreversible, a functional improvement can be obtained by rehabilitation. Thirty one cases of irreversible neurologic sequelae are reviewed.