The frequency distributions of the nuclear Feulgen-DNA, obtained with cytophotometric technique, in different types of female mammary carcinomas (invasive ductal carcinoma, papillary and mucinous ductal carcinomas and invasive lobular carcinoma) were correlated with the histological diagnoses and with the age of the patients. The highest and broadly scattered values of nuclear Feulgen-DNA content, in agreement with the cytomorphologic pictures, were observed in the invasive ductal carcinomas, above all in the youngest subjects (values from 2c to 16c). Papillary and mucinous ductal carcinomas from subjects of the same age, showed lower values; the cases of invasive lobular carcinomas exhibited more homogeneous values with a higher number of cells in the 2c region. The tissue with histological normal patterns showed 2c values of Feulgen-DNA contents with some values near 4c. The general situation point out a different complexity of the tumor population which can be related to a mosaic composition and/or to a multifocal origin with presence of cycling, non-cycling, euploid, aneuploid and polyploid fractions. Then, the Feulgen-DNA content can be correlated to the tumor type and the patient age; it is useful for diagnostic and prognostic problems in the oncological field.