Clinical and electroencephalographic evolution, as well as the neuropathology, are described in a 25 year old man with a Hurst's acute haemorrhagic leucoencephalitis. Lesions, unusually symmetrical, coexists with those, without vascular necrosis nor haemorrhages, of the perivenous encephalomyelitis. The aspecific onset, course and results of complementary investigations appear on reviewing 44 clinical observations in the literature. Histologic examination of affected white matter is the only was to assess the diagnosis. Two features that may have been previously neglected are outlined: the predilection for 20 to 40 years old males, while the adolescent male, the most susceptible to perivenous encephalomyelitis after specific fevers, is not affected by Hurst's disease. Multiple sclerosis or a prodromal meningo-encephalitis, clinically undetected, could be not rare. Therapeutic results of surgical decompression, hyperosmolar substances and massive doses of corticosteroids (3 survivals out of 10 cases diagnosed on biopsy) cannto be evaluated at the present time. By analogy with the simple and the hyperacute forms of EAE, the myelinotoxicity may result from sensitized lymphocytes alone in the perivenous encephalomyelitis, from an association of circulating antibodies and lymphocytes in Hurst's disease. Whether the immunoglobulins enchance the cellular myelinotoxicity or induce an immune complex disease upon a perivenous encephalomyelitis is still to be determined.