To clarify the mechanism of the cellular DNA-breaking reaction of epinephrine (Ep), we examined the interaction between Ep and chromatin components. The Ep-binding activity of histone increased after the dissociation of histone subunits. The Ep bound to DNA increased with the increase of Ep concentration and pH. Solubilized chromatin, v bodies, showed Ep-oxidizing activity in the absence of Cu 2 +. The binding of Ep to v bodies occurred immediately after mixing and was highly specific. These data suggest the presence of some Ep-specific binding protein(s) in chromatin which oxidizes Ep and induces DNA breakage.