The word 'complex' has several meanings and synonyms such as composite, obsession, heterogeneous, mixed and network, can all be used in its place. Our obsession with bacteria from the Burkholderia cepacia complex started in the early 1990s. In less than 10 years, we have seen the status of this bacterium move from: (i) a lesser known pseudomonad opportunist pathogen, (ii) to devastating infections transmitted between patients with cystic fibrosis (CF), (iii) through divisions into several new species, and (iv) now on towards one of the largest gram-negative genome sequencing projects. For microbiologists, hospital infection control officers, caregivers, and most of all the CF community, the changes in our understanding of the taxonomy, epidemiology and pathogenesis of the bacterium 'B. cepacia' are complex.