GPI-anchored proteins, glpicosphingolipids, and sphhgomyelin are all enriched in the detergent-insoluble complex which has been suggested to be purified caveolae. I studied the relationship of the molecules with caveolae in cultured cells by i"unOcgt0chemical methods. In cells reacted with antibodies to various membrane proteins and lipids on ice and fmed More applying secondary antibodies, labeling did not show concentration in caveolae. In contrast, when cells were incubated with the primary and secondary antibodies on ice and then transferred to 37'C without fmtion, labeled Thy-1.2, p2-miaoglobulin, lactosyl ceramide, ceramide tetrahexose, Fomman antigen, and sphingomyelin became concentrated in caveolae, whereas labeled transferrin receptor did were sequestered in the same caveolae when crosslinked with not. Thy-1.2 and sphingolipids formed COIIUIIOII patches and