The expression of DNA ploidy, the cell cycle and Ki67 antigen in nasopharyngeal carcinoma (NPC) were studied and their relationship with the clinical biological behaviors and prognosis of NPC was evaluated. Biopsied specimens of NPC were made into cell suspension. By using cytometric double labeling Ki67 and DNA method, the expression of DNA ploidy, the cell cycle and Ki67antigen were analyzed. The patients were followed-up for about 3 years and the relationship between the above-mentioned parameters and the clinical biological behavior and prognosis of NPC were evaluated. Of the 62 cases of NPC, the DNA aneuploid accounted for 29.03 %. The S phase cells accounted for 0 to 54 % in the cell cycle and the positive expression of Ki67 ranged from 0 to 52 %.There were 40 cases of LPI (64.5 % ) including 15 negative cases and 22 cases of HPI (35.5 % ) respectively. The DNA anueploid content was positively related to the S phase cells. The patients having a low expression of Ki67 or DNA aneuploid in tumor cells were not sensitive to chemotherapy, liable to metastasis to distant organs and had a poor prognosis, while Ki67 showed no correlation with DNA ploidy and the cell cycle. It was suggested that DNA ploidy and Ki67 could be used as an independent and objective marker to evaluate the radiosensitivity and prognosis of NPC.