An indirect immunofluorescent assay to detect antibodies against the lipopolysaccharide (LPS) of Burkholderia pseudomallei and taxonomically closely related species was developed with the Luminex system. LPSs of Pseudomonas aeruginosa, Burkholderia cepacia, Burkholderia thailandensis, Burkholderia vietnamiensis, B. pseudomallei, and Burkholderia mallei were successfully conjugated to Luminex microspheres. Antibodies measured against the LPS of B. pseudomallei-conjugated Luminex beads only cross-reacted with those of two genetically closely related species, B. mallei and B. thailandensis (previously classified as non-pathogenic arabinose-negative B. pseudomallei). However, this system could distinguish other closely related species from B. pseudomallei. This assay is able to detect significantly high levels of anti-LPS antibodies of B. pseudomallei in serum from patients with culture-proven melioidosis.