The effect of metallothionein (MT) on hydroxyl-radical-induced DNA damage was investigated in an in-vitro study. The degradation of DNA as demonstrated by agarose gel electrophoresis was inhibited by MT in a concentration-dependent manner. The degradation of DNA was almost completely inhibited by a concentration of 13 microM MT, whereas a concentration of 10 mM glutathione was needed to achieve the same protective effect.