We recently described a monoclonal antibody (clone 27A) that detected a membrane antigen specific for glomerular podocytes in adult rat kidney. After binding in vivo, the antibodies induced rapid changes in the foot processes. Here we show that in other rat tissues the antigen is detectable only in cells of adrenal medulla, in some cells of neural or neural crest origin, and in 1 to 5% of the cells of a rat pheochromocytoma cell line PC-12. Attempts to isolate the antigen revealed that it is an acidic, sialic acid containing lipid, as shown by thin layer chromatography and immuno-overlay techniques. Further characterization of the gangliosides extracted from rat glomeruli, bovine kidney, rat adrenal glands, or from PC-12 cells by ion exchange, thin layer, and gas liquid chromatography identified the antigenic lipid as a modified disialosyllactosylceramide (GD3). The results of mild alkaline treatment or periodate oxidation of the antigenic ganglioside, as well as chemical O-acetylation studies of standard gangliosides, showed that the modified ganglioside is O-acetylated, most probably at the 9-carbon of its terminal sialic acid residue. To our knowledge this is the first report of cell-type specific expression of gangliosides in the kidney.