A new method is described for the determination of brain gangliosides by measuring stearic acid, the chief acid of gangliosides, in an appropriately purified brain extract. The method includes extraction of tissue with chloroform-methanol, extraction of gangliosides from the extract with 0.1 M KCl, evaporation of the aqueous phase, methanolysis, and gas-liquid chromatography of the resultant methyl esters with a double internal standard. The method depends on the simple composition of ganglioside fatty acids (80% stearic acid) and allows determination of less than 0.05 micromole of gangliosides. Interfering lipids are removed from the ganglioside extract by washing with chloroform-methanol-water. The effects of contamination with nonlipid N-acetylneuraminic acid are avoided.