Several antibiotics were examined for their potential to eliminate mycoplasmas from contaminated cell cultures. Acholeplasma laidlawii, Mycoplasma arginini, Mycoplasma hyorhinis and Mycoplasma orale were effectively eliminated from experimentally contaminated mouse fibroblasts and mink epithelial cells by the use of the antibiotics minocycline and tiamutin. An elimination procedure was established, which involved the consecutive treatment of the cultures over a period of 3 weeks, followed by cell cloning. This procedure was effective when applied to cell lines which had been contaminated with unidentified and partially non-cultivable strains of mycoplasmas.