In the previous report, we have reported that Clostridium sp. TU-15A is a powerful polymer producing microorganism and has been selected as a candidate for MEOR (Microbial Enhanced Oil Recovery). This microorganism grows easily in the molasses medium and increases the viscosity of the culture solution up to 70 cP (at 38.3s-1) or higher by a 10 day cultivation.In the present study, two different sets of flooding experiments were conducted for evaluating the effect of TU-15A on displacement efficiency and sweep efficiency. One was for the different pressure gradient experiment and the other was for the anisotropic permeability experiment. The former experimental system consisted of a pair of two independent sand packs with different length (ratio of length is 1 to 1.4) but with the same permeability, connected in parallel for simulating between the highest and the lowest in a five spot water flood pattern. The other consisted of a pair of two independent sand packs of different permeabilities but with the same length, connected in parallel for simulating the anisotropy of reservoir permeability. In these sets of experiments, the high viscous culture solution of TU-15A was injected after water flood experiment, as a tertiary mode and the improved oil recovery were observed.In the different pressure gradient experiment, the fraction of flow rate into the long sand pack was improved from 22% to 47% by injection of the culture solution of TU-15A, which led to the increase of oil recovery from 69% to 87% in the long sand pack. In the anisotropic peameability experiment, the oil recovery was increased in the low permeability sand pack from 56% to 80%, which was attributed to the modification of flow rate into the low permeability sand pack from 8% to 22% by the injection of the culture solution of TU-15A.Results obtained in these experiments imply that TU-15A can be utilized for MEOR.