Human leukaemic lymphocytes of the common acute lymphoblastic leukaemia (cALL) subtype were analysed for ganglioside composition by over pressured layer chromatography-densitometry. Two major ganglioside components, GM3 (58.0-77.8% of the total sialic acid content) and GM1 (20.7%-29.2%), and some minor compounds, GM2 (trace amounts to 9.6%) and unidentified gangliosides with chromatographic mobility between GM1 and GD1a (trace to 12.6%), were isolated from these cells. The relative amount of GM3 in cALL cells was found to be about double that in normal lymphocytes (65.7% vs. 37.7%), but lower than in chronic lymphocytic leukaemia (CLL) cells (65.7% vs. 81.5%). The cALL cells contained trace amounts of the ganglioside GD3, a compound present in CLL cells (5.6%) but absent in normal lymphocytes.