AbstractMesenchymal cells from the prefusion human embryonic palate have been established in culture and can be grown in either a serum‐free hormone‐supplemented medium or a serum‐containing medium. The growth of these cells is quite rapid in culture and inhibited in a dose‐dependent manner by most teratogens thus far tested, such as dexamethasone. These cells are highly sensitive to a variety of DNA synthetic and mitotic inhibitors. The responses of these cells are complementary to the ovarian tumor cell attachment assay of Braun et al [1, and in this volume]. When used in conjunction with the tumor cells, the overall reliability is greater than 90% with only one false‐negative, al