Permanently growing cell lines can be invaluable because of their usefulness in a variety of experimental situations. We report the characteristics of seven cell lines designated, SNU-306, SNU-334, SNU-1528, SNU-1553, SNU-1581, SNU-1958 and SNU-2372, which were established from three primary carcinomas, two pleural effusion, one pericardial effusion and one ascitic fluid samples obtained from seven Korean breast carcinoma patients. The histopathology of the primary tumors and their in vitro growth characteristics are described. DNA fingerprinting analysis and genetic alterations in the p53 and EGFR genes were conducted. The expression levels of the ER-α, PR, C-erbB2, E-cadherin, COX-2, MDR and MXR genes were investigated and sensitivity to anticancer drugs was screened. Growth was as adherent cells (four cell lines), floating aggregates (one cell line) and both (two cell lines). All lines were free of mycoplasma or bacteria and were proven unique by DNA fingerprinting analysis using 18 microsatellite markers. Estrogen receptor (ER) mRNA was highly expressed in five cell lines and low or undetectable in SNU-1958 and SNU-2372. Progesterone receptor (PR) mRNA was expressed only in the SNU-306. SNU-1958 and SNU-2372 were hormone receptor-negative and C-erbB2-negative (triple-negative). SNU-1528 had an in-frame deletion of 42 base pairs of p53 gene and showed over 20-fold resistance for taxol compared to the other cell lines. There were no mutation in the EGFR gene; COX-2 was expressed in four cell lines and MXR was expressed in two cell lines. These well-characterized seven breast cancer cell lines, which include two triple-negative cell lines, will be useful for the study of breast cancer biology.