The gangliosides of male rat dorsal root ganglia were studied during aging from the first day postnatally until senescence at 24 months. The ganglioside contents increased drastically until 12 months after birth and thereafter did not change considerably, and the increase pattern was in parallel with the increase of wet weight of the tissues. The major gangliosides of the dorsal root ganglia were GM3, LM1 (sialosyl-lactoneotetraosylceramide), unknown ganglioside X, GD1a, GD1b, GT1b and GQ1b. The most drastic changes in ganglioside composition were observed between the ages of postnatal day 1 and 1.5 months. The unknown ganglioside X (dominant at postnatal day I) decreased up to 1.5 months. In contrast, LM1, a minor ganglioside postnatal day 1, increased until 1.5 months of age. Except for these changes, the other gangliosides were present at almost constant ratios in the component profiles during aging until senescence.