Nuclear DNA ploidy pattern was examined in 22 breast carcinomas with a tumor mass of up to 2.2 cm and compared with the clinical and histological parameters of the malignant potentiality of breast carcinomas. The 22 carcinomas were divided into 11 aneuploid and 11 near-diploid carcinomas. It was found that the histological type, histological grade, nuclear grade, mitotic index and lymphatic invasion were either only slightly, or not correlated at all with the DNA ploidy pattern. Nevertheless, lymph node metastasis and negative estrogen receptor status was more frequently seen in the patients with aneuploid carcinoma than in those with near-diploid carcinoma.