To overcome problems associated with Western blotting of denatured proteins, we have used quantitative immunoelectrophoretic techniques to perform functional analysis of the Neisseria gonorrhoeae common antigen. Using these techniques, we show (a) that Neisseria gonorrhoeae expresses an antigen that is cross-reactive with the common antigen of Pseudomonas aeruginosa and Legionella micdadei and with the GroEl-like protein of Chlamydia, and (b) that this N. gonorrhoeae common antigen has lectin-like activity and can be precipitated with three different sugars immobilized on agarose beads: alpha-D-glucosamine, maltose and fucose.