We reported two respirator-aided 10-year-survival male patients with sporadic amyotrophic lateral sclerosis (ALS). Their ages at onset were 54 and 52, clinical features common in both cases, the durations to tracheotomy 32 months and 27 months respectively, and the durations for respiratory support over 8 years in both cases. There were normal external ocular movement, normal pelvic sphincter function, normal sensory system and no bed sores throughout 10 years of illness. The brain weighted 1,295 g in case 1 and 1,430 g in case 2, being normal macroscopically. The spinal cord was slightly wasted with atrophic anterior roots. The histopathological study demonstrated the typical pattern of ALS in spite of the prolonged survival with artificial respiration. Neuronal loss and gliosis of the motor nuclei in the spinal cord and brainstem were more striking than those of the natural course. Neither hypertrophic astrocyte, central chromatolysis nor neuronophagia was observed. This finding suggested inactive condition of the degeneration. The pattern of white matter degeneration in the cord indicated some pallor of anterior and lateral columns, severe pallor of pyramidal tracts and intact posterior column and spinocerebellar tracts. The giant pyramidal cells in the precentral gyrus were lost in both cases. Pyramidal degeneration was traceable up to the cerebral peduncles in the case 2 and undetectable in that portion in the case 1. On the other hand, the extraocular muscle nuclei, the Onuf's nuclei, the dorsal motor nucleus of the vagus nerve, intermediolateral and Clarke's nuclei were relatively preserved, though no cell count was done in Clarke's nuclei and Onuf's nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)