Myelins of the PNS were isolated from human motor and sensory nerves of cauda equina, and their ganglioside compositions were compared. The predominant ganglioside in the human PNS myelins, both from motor and sensory nerves, was LM1 (sialosylneolactotetraosylceramide). Sialosyl-nLc6Cer and disialosyl-nLc4Cer, GD3, GM3, and GD1b were detected as common components of the two nerve myelins. Furthermore, it was revealed that the motor nerve myelin contained GM1 (about 15% of total gangliosides), whereas sensory nerve myelin contained only a trace amount of GM1 (less than 5%), by TLC analyses together with TLC immunostaining using anti-GM1 antibody. As for the disialoganglioside fraction, the content of GD1a, as well as that of GM1, differed in motor and sensory nerves. Thus, the different contents of the ganglioseries gangliosides in human motor and sensory nerve myelins were demonstrated.