Infections of the central nervous system may provoke glial and autoimmune responses but a definitive linkage between these infections and the pathogenesis of chronic neurologic disorders is still elusive. There are controversial reports implicating infectious agents in the pathogenetic mechanisms of chronic or long-term neurologic disorders, such as multiple sclerosis, amyotrophic lateral sclerosis, Parkinson's disease, Alzheimer's disease and autistic spectrum disorders, but the specific role of bacterial or viral infections in the pathogenesis of these medical entities has not been fully elucidated. Up till now, the evidence is distant from definite, but certain cases may be attributed to infections in the millieu of multiple toxic events such as trauma, nutritional deficits, immune dysregulation and excitotoxicity in genetically vulnerable indiniduals. There is an ongoing debate concering the direct involvement of various infectious agents in the neurodegenerative and neurobehavioral diseases pathogenesis and/or their contribution to the deterioration of the disease or co-morbidity in these patients. These patients are exceptionally difficult to be treated by using single therapeutic modalities, because their disese is multifocal and treatment is aimed to control signs and symptoms rather than the true causes of the disease and its progressive course. Furthermore, even if these causative links were indetifiable, our therapeutic interventions would come too late due to the irreversible damages at the time of the initiation of treatment. Our aim is to comprehensively review all available data suggesting that infections could be common antecedent events of progressive neurologic degenerative or behavioural diseases.