To investigate the effect of cisdiammine-dichloroplatinum (cisplatin, CDDP) on rabbit VX2 tongue cancer, the relationship between the amount of CDDP accumulation in the tissue after CDDP administration by particle induced X-ray emission (PIXE) and the morphological changes of blood vessels was explored.VX2 cancer cells were transplanted into the marginal region of tongues of male Japanese white rabbits. On 3,7and 14 days after transplantation of cancer cells, 4 mg of CDDP was administered via the auricular vein once a day for various periods of one time, 3 times for 3 consecutive days and 5 times for 5 consecutive days. The animals were sacrificed 24 hours after the end of each administration period. The tongues, deep cervical lymph nodes and kidneys were removed and embedded in paraffin according to the common procedure used to prepare serial sections of 30 μm and 5 μm thickness altemately. The 30μm sections were used to determine the CDDP accumulation by PIXE and the 5 μm sections were used to measure the ratio of blood vessel per area, the number of blood vessels and tongue tumor volume.The accumulation of CDDP, ratio of blood vessels area and number of blood vessels increased during the period from 3 days to 7 days after transplantation as the tumors grew. However, they decreased on 14 days after transplantation because of necrosis in the central part of tumors. The increases of CDDP accumulation inhibited the increasing tendency of tumor volume. The half-life of CDDP accumulation was estimated to be about l day after administration. The accumulation of CDDP in the deep cervical lymph nodes increased with the times of administration, although no morphological change in the blood vessels was observed. The CDDP accumulation in the kidneys also increased with the times of administration without any change of blood vessels, although atrophia of the glomeruli and dilatation of the urinary tubules were observed.Thus, the accumulation of CDDP was associated with increases and decreases in the ratio of blood vessels per area and the number of blood vessels in the tongue tumors. However, such a relationship was not explicit in the lymph nodes and kidneys.