We established five murine monoclonal antibodies (MAbs) specific for a-pathway ganglio-series gangliosides by immunizing C3H/HeN mice with these purified gangliosides adsorbed to Salmonella minnesota, followed by fusion with mouse myeloma cells. The binding specificities of these MAbs were determined by enzyme-linked immunosorbent assay and immunostaining on thin-layer chromatogram. These five MAbs, designated GMR6, GMB28, GMB16, GMR17, and GMR11 reacted strongly with the gangliosides GM3, GM2, GM1, GD1a, and GT1a, respectively, that were used as immunogens. Three MAbs, GMB28 (anti-GM2), GMB16 (anti-GM1), and GMR11 (anti-GT1a) showed highly restricted binding specificities, reacting only with the immunizing ganglioside. None of the other various authentic gangliosides or neutral glycolipids was recognized. On the other hand, the other two MAbs, GMR6 (anti-GM3) and GMR17 (anti-GD1a) exhibited broader specifities. MAb GMR6 cross-reacted with GM4, GM1b, GD1a, GT1b, and IV³NeuAcα-nLc₄Cer. MAb GMR17 also reacted with GM1b and GT1b. Neither GMR6 nor GMR17 reacted with other gangliosides or neutral glycolipids tested. Using these MAbs, we determined the expression of these gangliosides, especially GM1, GD1a, and GT1a on mouse, rat and human leukemia cells. GM1 and GD1a were expressed on some leukemia cells, whereas GT1a was not detected in these cells.