The behaviour of an electrically heated carbon paste electrode (CPE) with the surface modified by a calf thymus double stranded (ds) DNA adsorption layer was investigated in the medium of a copper(II) complex with 1,10-phenanthroline (phen) as the chemical nuclease. Damage to DNA is affected strongly by the electrode temperature within the range of 22-38 degreesC as indicated by the square-wave voltammetric signals of the DNA redox marker Co(phen)(3)(3+) as well as the DNA guanine moiety. No significant effect of temperature on the binding constant was found at the titration of Cu(phen)(2)(2+) with dsDNA in solution. Thus, the formation of radical species and irreversible DNA damage are affected by DNA/CPE heating. The heated electrode can be applied advantageously to the real-time detection of traces of DNA-damaging agents.