A comprehensive history of Borna disease virus (BDV) and this infection, including the complete bibliography, is presented. Over the last 200 years, descriptions of this 'head disease' of horses ('Kopfkrankheit der Pferde') have been given. Considerable losscs in the horse population (< 0.8 Yo) led to intensive clinical and (neuro-)pathological investigations of t h s meningitis cerebmspinulis whch occurs with faint behavioural changes, occasionally followed by severe neurological symptomatology and death. The broad experimental host range reflects infections in nature which include horses, sheep, cattle, cats, dogs, rodents, ostriches, and some zoo animals. BDV infections are associated with phylogentically old brain areas, and the retina. Occasionally, expression in the autonomic nervous system occurs, besides its neurotropism BDV can spread to peripheral organs, especially to epithelial tissues and peripheral blood mononuclear cells. Infections of humans that can be monitored by antibodies, antigens or nucleic acids in blood samples are prominent features of future interest. BDV, the prototype of the family Bornuuiridae is an enveloped spherical virus carrying an 8.9 kb single-stranded, non-segmented RNA with negative polarity which replicates in the nucleus. These features together with its considerable genetic stability make this non-cytopathogenic virus an evolutionary 'old pathogen' in nature.