The presence of phytase activity was demonstrated in 26 strains of rabbit caecal bacteria. In 25 strains a low phytase activity, 0.10 ? 0.62 ?mol phosphate released per min per mg protein, was found. High activity (2.61 ?mol/min per mg protein) was foundin the strain identified as Enterococcus hirae. Phytase activity was cell associated, being higher in the cell extract than in the cell walls. Extracellular phytase activity and cell-associated phosphatase activity were not detected. Phytase activity was optimal around pH 5.0. Other bacteria with a high phytase activity may be present in the rabbit caecum but remain to be identified.