The new photosensitizer, we have helped to develop, PH-1126 has amine in the D-ring of pheophorbide structure. Comparing PH-1126 and hematoporphyrin derivative (HpD) in terms of the longest absorption peak of Q band, the wavelength of PH-1126 is 35nm longer. In terms of the absorption rate at the longest absorption peak of Q band with PH-1126 and HpD on same concentration showd the absorption of 10 value. Therefore, photodynamic effects using PH-1126 would probably be greater than those of HpD becouse of the distance of absorption band from that at hemoglobin. Comparing the fluorescence intensity rate of normal tissue to transplanted mice tumor tissues with i. v. injection and p. o. administration of PH-1126 taking the intensity of tumor fluorescence as 100% at 48 hour after administration, that of PH-1126 at i. v. injectiuon was 25.7 in skin, 20.9% in intestin and below 20% in other tissues, whereas PH-1126 of p. o. administration was 49.0% in intestin, 16% in stomach and below 20% in other tissues. The oral administration of PH-1126 showd the same tissue distribution as i. v. injection. After photodynamic therapy with Kr' laser (50mw, 30J/cm₂) following oral administration of PH-1126 (50mg/kg b. w.), the tumor decreased significantly.