Microfluorometric measurement of the DNA content of cell nuclei was performed on echo-guided aspiration specimens or imprints of operated fresh materials of fourty-one small thyroid papillary carcinomas of 10 mm or less in diameter and of six large ones more than 20 mm in diameter. The distribution patterns of the DNA content were classified into three groups: IIa, IIb and III. The DNA values in so-called sclerosing carcinomas mostly fell into Group-IIa, while ordinary papillary carcinomas were classified as Group-IIb and III. Our date suggests that the DNA microfluorometry of echo-guided aspiration specimens of small papillary carcinomas gives the index whether they will remain occult or not.