Misonidazole was histologically evaluated as a hypoxic cell radiosensitizer to a transplantable human cervical cancer in nude mice (Yumoto Strain). Acute exposure of X-ray (Lineac, a 1,000 rad dose) was applied to the cervical cancer. Tumor Volume (T.V. growth curve). Radiation alone induced an 8-10 day growth delay, but radiation therapy with Misonidazole induced a 10-12 day growth delay. Tumor Cord (T.C.). This idea originated with Thomlinson and Gray. They found that the radius of a tumor cord was always same. On the radiation therapy with Misonidazole, the tumor cords decreased faster than with radiation therapy alone. Tumor cellular Density (T.D.). This is the cell population per unit of area. We separated the tumor cords with two blocks, one near and one far from the blood vessel. T.D. decreased faster in the case of radiation with Misonidazole, and on the far square, radiation effectiveness was more obvious than on the near one. In addition, a histological examination proved that the Misonidazole affected hypoxic elements of the tumor, and this finding was proved in 48 hours after radiation. But aerobic elements of the tumor survived and were slightly changed histologically. In conclusion, Misonidazole proved to be an effective hypoxic cell sensitizer for human cervical cancer in radiation therapy.