Burkholderia cepacia complex (Bcc) is a group of phenotypically similar, genetically distinct bacteria that are beneficial to the environment but can also cause severe human infections. Bcc are being exploited for use as bioremediation agents and as a way to combat agricultural plant diseases. However, Bcc can cause lung infections in patients with chronic granulomatous disease or cystic fibrosis often resulting in mortality of these patients. Since it is unclear what bacterial components are necessary for causing human infections, studies of Bcc have focused on identifying putative virulence factors. As in other Gram-negative bacteria, the lipopolysaccharide (LPS) of Bcc induces a strong immune response that can contribute to host cell damage. The unusual structure of Bcc LPS lowers the anionic charge of the Bcc cell surface, which inhibits the binding and subsequent effects of cationic antibiotics. These distinguishing features include the substitution of a Ko for a Kdo residue in the inner core oligosaccharide and Ara4N residues bound to phosphates of the lipid A backbone. The structures of O antigen subunits and the consequent serotypes will also be discussed, with particular reference to the O antigen biosynthetic loci of two Bcc strains.