Objectives: MicroRNAs (miRNAs) have been underlined as a promising potential biomarker for breast cancer but are limited to tissue specimens. Clinical specimens of sera are more abundant and more conveniently collected than tissues. This work was designed to investigate the expression and correlation of a selected panel of miRNAs associated with breast tumor in tissues and matching serum samples. Methods: Tumor tissues, adjacent non-tumor tissues and matching serum samples were collected from 68 patients with newly diagnosed breast tumors. Normal control sera were collected from 40 healthy subjects. A panel of 6 miRNAs (miRNA-21, 106a, 126, 155, 199a and 335) were selected and their aberrant expression levels were quantified by using real-time PCR technique. Results: A high correlation of miRNA expression level was found between breast tumor tissues and sera. MiR-21, miR-106a and miR-155 were significantly over-expressed in the tumor specimens compared with those in normal controls (P < 0.05), whereas miR-126, miR-199a and miR-335 were significantly under-expressed (P < 0.05). Furthermore, the relative expression of miR-21, miR-126, miR-155, miR-199a and miR-335 was closely associated with clinicopathologic features of breast cancer (P < 0.05), such as histological tumor grades and sex hormone receptor expression. Conclusions: Selective expression and modulation of miRNAs could be potential blood-based biomarkers for breast cancer diagnosis, grading and prognosis. Our results should encourage further studies on the use of miRNAs in serum samples as an easy and convenient method of breast cancer screening. © 2010 Elsevier Inc. All rights reserved.