The distribution of urease-producing bacteria was examined in lumenal and mucosal-associated populations of the rabbit caecum. The total number of bacteria recovered on a nonspecific, semi-defined medium were 1,7 x 109 per g from lumen contents and 2,0 x 105 per g of washed, homogenized caecal wall. Urease activity was shown by 5,3% of strains isolated from lumen contents and 21,7% mucosal-associated strains. A higher proportion of bacteria associated with the caecal wall (63%) were facultative compared with 20% from the caecal content.