A selective cell culture medium, D-valine minimal essential medium (92 mg/l), has been developed to inhibit the proliferation of fibroblasts in cell culture (Gilbert & Migeon 1975). Substitution of D-valine for L-valine prevents fibroblast growth due to the absence of D-amino acid oxidase in these cells. Most cell cultures require foetal bovine serum as an essential component of the culture media, however foetal bovine serum contains L-valine, negating the value of D-valine selective media. To overcome this difficulty, we have produced a modified selective media for cell culture, by the dialysis of foetal bovine serum and confirmed its ability to inhibit fibroblast growth whilst still allowing the proliferation of epithelial cells in culture.