Thin-layer chromatography (TLC) was used for revealing the heterogeneity of lipopolysaccharides (LPS) from Neisseria meningitidis. A complex pattern consisting of at least 4 bands was achieved for the vaccine strain N. meningitidis 44 76 . The complexity remained unchanged after dephosphorylation, but removal of both phosphate and O-acyl groups simplified the pattern into two bands. The band patterns of LPS of strain 44 76 after growth in two different media were substantially different, but became identical upon dephosphorylation. Staining of LPS on TLC plates by use of immunotype specific monoclonal antibodies provided specific band patterns at high sensitivity. In addition to revealing structural heterogeneity, the TLC system may thus be used for characterisation and differentiation of LPS-specific antibodies.