Microbiological analysis of soils from a polycyclic aromatic hydrocarbon (PAH)-contaminated site resulted in the enrichment of five microbial communities capable of utilizing pyrene as a sole carbon and energy source. Communities 4 and 5 rapidly degraded a number of different PAH compounds. Three pure cultures were isolated from community 5 using a spray plate method with pyrene as the sole carbon source. The cultures were identified as strains of Burkholderia (Pseudomonas) cepacia on the basis of biochemical and growth tests. The pure cultures (VUN 10 001, VUN 10 002 and VUN 10 003) were capable of degrading fluorene, phenanthrene and pyrene (100 mg l−1) to undetectable levels within 7–10 d in standard serum bottle cultures. Pyrene degradation was observed at concentrations up to 1000 mg l−1. The three isolates were also able to degrade other PAHs including fluoranthene, benz[a]anthracene and dibenz[a,h]anthracene as sole carbon and energy sources. Stimulation of dibenz[a,h]anthracene and benzo[a]pyrene degradation was achieved by the addition of small quantities of phenanthrene to cultures containing these compounds. Substrate utilization tests revealed that these micro-organisms could also grow on n-alkanes, chlorinated- and nitro-aromatic compounds.