Cell lines are traditionally used as tools for in vitro studies of breast cancer. It is highly debatable however, because of the genetic drift that occurs in such long term cultures how representative these cell lines are of breast cancer in vivo. For this reason primary cultures are generally regarded as a better model. Here we have used a primary culture technique (Int. J. Cancer, 66 (1996) 551; Br. J. Cancer, 78 (1998) 1421) to obtain primary breast cancer cells from 13 breast cancer biopsies. We then describe the development and use of methodology to confirm the purity of the cultures. The acquisition of a highly pure population of epithelial cells was confirmed by flow cytometric analysis of intracellular vimentin and cytokeratin 19. The methodology described will have many applications in studies requiring a highly pure population of epithelial breast cancer cells, as well as wide use in other cancers.