Nuclear DNA content was measured using a flow cytometric method to analyze 36 paraffin- embedded and 7 fresh tissues of 43 papillary carcinomas of thyroid gland. DNA aneuploidy was found in 3 cases(6.9%) and diploidy in 40 cases(93.1%). But there were no suggestive findings in clinical history, and cytological and morphological features for aneuploidy. In 40 diploid cases, S-phase fraction(SPF) were analyzed with regard to sex, age, tumor size, presence or absence of capsular invasion, lymph node involvement and ground glass nuclei. Among the multiple factors, only the tumor size, especially the larger sized-group(above 2cm in tumor diameter) was found to have a statistically significant higher SPF than the smaller sized-group (p<0.05). And high SPF groups relatively well corresponded to the high risk group. Thirty nine cases of papillary carcinoma have also been evaluated for proliferative activity with Ki-67 monoclonal antibody. The average Ki-67 labeling index was 0.36% in total cases, and that of the aneuploid cases was 0.73%, which was higher than that of the diploid cases(0.33%). So. We think that the low aneuploid rate and low Ki-67 labeling index relatively well represent the usual good clinical course of this tumor and the high SPF is a suggestive finding for a high risk group.