Cerebrosides, the representative sphingolipid in mushrooms, were isolated and purified from seven fruiting bodies of basidiomycetes, and their principal sphingoid base was confirmed to be 9-methyl-4-trans,8-trans-sphingadienine (9-methyl base). The 9-methyl base was also present in free ceramide, diglycosylceramide (diglucosyl type) and the acidic sphingolipid (phosphorylinositol-containing sphingolipid) fraction from the Maitake mushroom (Grifola frondosa), although usually in small amount. Examination was also made of the effects of fungal cerebroside on the fluidity of phospholipid liposomes by fluorescence depolarization of the hydrophobic fluorescence probe (1,6-diphenyl-1,3,5-hexatriene). The 9-methyl branched chain in fungal cerebroside molecules, as also with cis double bond in sphingoid base or fatty acid moieties, was found to effectively inhibit decrease in liposome fluidity as a result of cerebroside (30%) addition. The 9-methyl base in fungal cerebroside should thus have the same physiological functions as 8-cis unsaturated sphingoid bases in plants.