The aim of the present project was to quantify the level of plasma DNA in patients with malignant or non-malignant breast diseases and in healthy controls, then investigate whether such measurements have diagnostic or prognostic value. Plasma DNA from 121 women (61 patients with breast cancer, 33 control patients with benign breast diseases and 27 healthy control individuals) was quantified by a real-time quantitative polymerase chain reaction (PCR) method. Plasma DNA concentration in the breast cancer patients (median 65 ng/ml) was significantly higher (P<0.05) than that in the control patients (median 22 ng/ml) or healthy control (median 13 ng/ml). No association was observed between plasma DNA levels and clinicopathological parameters. The data suggest that quantification of plasma circulating DNA may be a valuable complementary diagnostic tool in discriminate breast cancer from unaffected individuals and may be proposed as an early detection test as well as a new, noninvasive assay to follow-up patients.