A BAC library of 30,228 clones with an average insert size of 102 kb was constructed in the grass Brachypodium sylvaticum. Brachypodium has a simple genome, similar in size and repetitive DNA content to that of rice, and is more closely related than rice both to the major temperate cereals wheat and barley, and to the forage grasses. The library represents 6.6 genome equivalents, implying a 99.9% probability of recovering any specific sequence. The library was arrayed onto two high-density colony filters, which were screened with heterologous DNA probes from rice chromosome nine and from syntenous regions of wheat, barley, maize and oat. The construction of Brachypodium BAC contigs revealed that synteny between rice, wheat and Brachypodium was largely maintained over several regions of rice chromosome nine. This suggests that Brachypodium will be a useful tool in the elucidation of gene content in agronomically important cereal crops, complementing rice as a "grass genome model".