Hallucinations (mainly visual), psychosis and excessive daytime sleepiness are potential side-effects of dopaminergic treatment. They may require a reduction or suppression of dopaminergic agonists, and the prescription of atypical neuroleptic agents or vigilance-enhancing drugs. The recent description of narcolepsy-like sleep onset in rapid eye movement sleep periods synchronous with hypnagogic hallucinations in patients with dopaminergic-induced psychosis or excessive daytime sleepiness, suggests that the mesodiencephalic lesions may predispose to the psychic effects of dopaminergic treatment. Disease-related mood disorders, sexual compulsions, gambling or levodopa addiction may also be amplified by the antiparkinsonian treatment. These complications illustrate the neuro-psychic aspect of Parkinson's disease: psychic troubles may result from a subtle balance between the direct effects of drugs, the pre-morbid pathological personality and the cortical and subcortical lesions.