The ganglioside mixture from the cerebellum of young, 6 month old and two years old rats, was fractionated by reversed phase high performance liquid chromatography, each ganglioside homogeneous in the oligosaccharide chain as well as in the long-chain base being subsequently quantified. Two long-chain bases, LCB, were components of the five major gangliosides GM1, GD1a, GD1b, GT1b and GQ1b, these being the C18:1 LCB and C20:1 LCB. The content of C20:1 ganglioside molecular species was lower than that of the C18:1 one. In very young animals, day 8, the C20:1 ganglioside species represented about 8% of the total ganglioside content, then they progressively increased and reached, at 2 years, about 42% of the total. C18:1 GD1a and C18:1 GT1b, were the major species in young animals and reached their highest content at day 29, being 1.45 and 1.28 nmol/mg protein, respectively. The content of these two species decreased in adult and old animals and at two years it was 0.71 and 0.82 nmol/mg protein, respectively.