To investigate the role of BRCA1 and BRCA2 mutations in Korean patients with sporadic breast cancer, 793 breast cancer patients were analyzed by denaturing high performance liquid chromatography and direct sequencing. The 793 breast cancer patients enrolled in this study had no family history of affected first- or second-degree relatives with breast and/or ovarian cancer. Seventy-nine different sequence variations were identified, of which 34 were novel. Fifteen deleterious mutations were detected in 20 out of 793 patients (2.5%): 11 frameshift mutations and 4 nonsense mutations (seven in BRCA1 and eight in BRCA2), and no recurrent or founder mutations were observed in BRCA mutation screening. However, three mutations (K467X, 3972delTGAG, and R2494X in BRCA2) were identified in other studies of the Korean population. Of 793 patients, the clinicopathological information was obtained in 135 patients, who included 20 deleterious mutation-positive and 115 deleterious mutation-negative groups. The median age at diagnosis, histologic type, histologic grade and T stage did not show statistically significant difference between these two groups. BRCA-mutation-associated tumors showed lower estrogen receptor, progesterone receptor, and HER-2/neu but higher p53 expression. Although poor prognostic features were noted in BRCA-associated tumors, we did not find statistically significant differences. The present study will be helpful in the evaluation of the need for the genetic screening of germline BRCA mutations and reliable genetic counseling for sporadic breast cancer patients.