The influence of three categories of anti-cancer agents on competence development and on the binding of homologous DNA to cells have been studied in the Bacillus subtilis transformation system. Treatment of cells developing competence with testolactone resulted in a slight enhancement of transformation at high doses (50 and 100 μg/ml) of the drug, but this process was inhibited at 25 μg/ml. DNA binding was unaffected by this drug. DNA-interacting agents (daunomycin, prospidine, peptichemio and mithramycin) usually inhibited DNA-mediated transformation in a higher extent than DNA binding. Antimetabolites of DNA synthesis were also tested: dacarbazine did not greatly inhibit the binding and expression of donor DNA. 5-Fluorouracil appeared to slightly enhance transformation at low levels (1 μg/ml), although it was inhibited at higher dos