A new method for the identification of oligosaccharides obtained by enzymatic digestion of hyaluronic acid (HA) with bacterial hyaluronidase (HA lyase, E.C. 188.8.131.52, from Streptococcus agalactiae) using online capillary electrophoresis/electrospray mass spectrometry (CE/ESI-MS) is presented. A fused-silica capillary coated with polyacrylamide was used with a 40 mM ammonium acetate buffer at pH 9.0 and a separation voltage of +30 kV applied to the inlet. Separation was achieved for oligosaccharides containing 4–16 monomers. The migration behavior follows the chain length of the oligomers, regardless of charge state. However, no linear relationship was found for the relation between mobility and chain length. Using an ion trap mass analyzer, complementary structural information was obtained by MS/MS and MSn experiments. Copyright © 2003 John Wiley & Sons, Ltd.