The glycosphingolipid pattern was examined in three cases of late infantile metachromatic leukodystrophy (MLD): one with a relatively short (2.5 years), one with a long (7.8 years), and one with a very long (13.2 years) survival time. All values were compared with those of age-matched normal controls. The cerebroside concentration was reduced to 25, 12, and 4%, respectively, in the MLD white matter, whereas the sulfatide concentration was increased up to 200% of the control value. The yield of myelin was reduced to less than 15% in the early case and to less than 3 and 1%, respectively, in the two later cases. There was no sign of increased sulfatide proportion in the myelin. The ganglioside pattern was normal in cerebral gray matter, but in the white matter, contents of gangliosides of the lacto series were significantly increased, in particular, the ganglioside suggested by us as being characteristic of reactive astrocytosis. For the first time, lysosulfatide was identified in MLD and normal human brains by mass spectrometry and radioimmunoaffinity TLC using specific monoclonal antibody. Its quantity was found to be similar in normal and MLD brains. These findings support our postulation that the lysoglycosphingolipids are synthesized de novo from sphingosine and that they do not play a key role in pathogenetic mechanisms.