The diversity of bacteria present in the caecum of the rabbit was investigated. Partial bacterial 16S rRNA genes from a digested sample collected from the caecum of an adult rabbit were amplified by PCR. Sequence analysis of the amplified fragments indicated highest similarity was to bacterial sequences previously described from other gut environments. However, only one sequence showed significant identity (97% threshold) to any previously described bacterial 16S rRNA genes. Furthermore, most of the sequences clustered together in groups lacking representatives from sequences already described, suggesting that the rabbit caecal flora contains organisms not previously described.