Adriamycin-Fe(3+)-induced lipid peroxidation was enhanced by ascorbate at low concentrations. High concentrations of ascorbate also enhanced the peroxidation reaction, but only at an early stage. The initial rate of peroxidation depended upon the ratio of adriamycin-Fe2+/adriamycin-Fe3+ and the maximum rate was observed at the ratio of 1:1. These results suggest that the adriamycin-Fe(3+)-induced lipid peroxidation may be initiated by an adriamycin-Fe(2+)-oxygen-adriamycin-Fe3+ complex. Ascorbate also promoted bathophenanthroline-Fe2+ formation from adriamycin-Fe3+ in a dose-dependent manner. It seems likely that ascorbate influences the peroxidation reaction via the reduction of adriamycin-Fe3+. During the interaction of adriamycin-Fe3+ with ascorbate, deoxyribose was not degraded, suggesting that hydroxyl radical formation did not occur. In contrast, plasmid PM2 DNA was readily damaged during the interaction of adriamycin-Fe3+ with ascorbate. Catalase, mannitol and dimethylsulfoxide prevented DNA damage. No DNA damage occurred when the reaction was run under nitrogen gas, indicating that oxygen is involved.